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Now that you have learned how to step in to functions and step out of functions, how to do it do and

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also how to insert and delete comments, let us continue the analysis of this crime.

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And so this is the main function.

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Over here, if your argument is going is not to he, will you show you the usage and once you enter

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usage, you a senior program.

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So I enter the usage.

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Now, after printing the usage message, you can't actually function to exit the program and you will

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not continue.

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Let's step out of commission, but let's assume you into two arguments.

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So in this case, you have two arguments, Fi, followed by serial number.

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So he satisfies this argument.

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So this Paganistic, you can go to the next line and call another function checks here.

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Taxidriver, past the security that you enter, which in this case is one, two, three, four, five,

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six, seven.

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Argument one, a hard one is actually your silkie, just like Humvee's zero is your binary name, Sify.

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So now let's go inside and see what this thing does.

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So to enter the step into the function, the double click on it.

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And here we see chaar.

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So, you know, the CHA premise of the one.

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Just checking in, hitting back, I'll be one so we can certainly do this and rename this ASV one.

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So right, click on this and then the new variable is

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the one.

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Oh, if you want to be more descriptive, you can say ritzier.

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So you know that this is a serious killer issue into.

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And then in here, you used to streamline function to count the length of your key visitor, and he

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would start the result in there as well.

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So from here, Venona as well, one must be the length we can rename it likely and rename the variable

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length.

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So now when you click the link, you highlight all the similarly selected Verba label.

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And you can see this light is being used in multiple places in this function.

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Now, on the next line, which is nine, 10, if we don't check whether your line is equal to zero one

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zero.

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Your X prefix means that this is hexadecimal, so to convert this into a decimal number, you can use

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a calculator.

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So the program is calculated and for tax hikes and in typing here in zero one zero one zero and click

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on this month and it is 16.

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So now we know that this is 16.

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It is checking if the length is 16.

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So it's a 1916 Nanjo serial number line is correct.

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So this suggests that he wants us to enter a certain number, which is 16 characters long.

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So we can actually work on reducing to to show decimal number, so to convert this, to show decimal

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number, selling this by clicking this and then go to the disassembly view and look for it, here is

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how to like blue.

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Whatever you click here will be highlighted in light blue.

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For example, if I click on this, you highlight this, if I click on this, you had any spot.

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So if I wanted to select this, I click on this and you highlight this spot in light blue.

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So now I can click on this and select convert from the bottom here and then select.

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Signed this 16, so I like this one and there is no negative number.

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It is only positive numbers.

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So now you can see once you converted, convicted in the disassembly view, it is also changed and reflect

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it in a different part of you.

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Now it's easier to read.

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And then next one would be the wall.

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The wall in this case.

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Access to parameters, and he is quite unique.

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Wallop can have one barometer or can have two parameters, so while in this example, the world accepts

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two parameters.

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So in this case, the first parameter, they says, is to assign something to length.

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So in this case, it is assigning the length of the serial number.

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And then maybe the lanky 16, for example, and then the second parameter here it is checking whether

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local one sees less.

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So here is checking local one see is less and less.

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So how do we understand the meaning of this?

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Notice that the first perimeter is separated from the second perimeter with a comma, that means they

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will perform this instruction first, then only do this instruction.

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So in this case here, the first instruction is just to assign 16 to the line, because we know that

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it requires your line to be 16 to definitely three in line to return 16.

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So this will not change the operation on the wall, the volume will continue to move on to the second

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second parameter.

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Now you will check whether once he is less than 16, if he is not insisting, he enter into the loop

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inside here.

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If you look over and see he is not equal, if not last in line, then you will quit.

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So this is how you can understand.

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So the first parameter is merely expression to perform some assignment you can actually is similar to

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writing in line outside here.

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And then taking away this spot,

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so is a cemetery, see?

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All right, so in this case here, the decompiled the compiler has put the D Tamlin in a while, saying

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separately with a comma separated, a comma with a second parameter.

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So he performed the selection.

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So now what is this little girl?

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And she just ignores the long Ulong here.

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The important part is the variable name.

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So what is local?

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Once you do when you click on one C, it will highlight only occurrences on the currency and you can

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notice something here.

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Look up.

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He is using, say, every element.

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So you suggested you go and see his array index and you can confirm it by looking out here.

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Here is where you increase the value of the index by two and then go back to look again and check whether

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it is still linked.

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So this is just a way of going through every element of the array, the Array Zero series.

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And he said no.

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He says here a key which you enter.

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So knowing that this is a very nice we can rename it correctly and rename it as her index.

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This makes it easier to understand how when you are doing analysis, so now we know that it is now checking

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in here, the 15 is checking whether the is correct or the array minus.

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The next character, because is plus one here and then the new minus, the second character from the

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first character is a result not equal to negative one.

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If he's not good court, they define the initial serial number, he's wrong.

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Immediately he will return.

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That means I see the look.

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So this is the algorithm for your Cerutty.

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And this is what it means, what it looks like.

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So now I use I to represent reenacts, so that's easier to it's easier to read.

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So in this case here.

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It is trying to compare whether the first character, minus the second character is not equal to negative

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one.

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So assuming that I enter zero number like this.

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I when you first enter, will be zero, Silvani zero is assessing a first zero key character and he

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will take that first character, minus I plus one.

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Plus one is a second tier key character.

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So it's trying to check.

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Right.

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The one minus two is to go to negative one.

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If it is not, then we will quit by returning.

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He will not proceed with the rest of the loop.

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So they suggest that in order to enter the character, your first character must be the second character

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by one.

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So then you minus one, minus two, he will get 91.

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After that, he will go down here and then he will increase your index by two.

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So an increase in do he will now become too high will be too.

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When he first ran, I was zero now, because you plus two eyewitness to.

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So now you it's zero to minus zero three, it means he will take zero to.

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Minus zero, three and C, very negative one.

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Zero two refers to this three zero zero zero one zero one one zero two is this one.

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OK, so I do miss tree, the tree, you take three minus four and they check, all right.

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So because three minus four is negative one, that means you're correct.

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Then he will go and increase the index by two again, and then now when to test four in five.

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So four and five refers to zero.

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One, two, three, four.

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These two five nine six.

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So finally, he's 91, increased by tulgan, so we check seven minus, he's a negative one.

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Yes, he is.

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Then you increase by two again, the ME check this, and this is in 91.

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Yes, he still 81.

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So you must make sure that after it you must start from one again so that when you minus one, minus

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two, you still get ninety one and then the total line must be 16.

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So this is your password.

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This is a security.

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OK, so now you can see there you go to here and you type in one, two, three, four, five, six,

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seven, eight.

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One, two, three, four, five, six, seven, eight, 16 characters, again, enter and you get good

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here.

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So that is trysting here.

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Now, how does he get you to notice here if you're any time he checks in, find it the moment he detects

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that the.

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To Syria is wrong.

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He return this no what is this number have in hexadecimal notation o f means negative one.

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It is based on the two complement notation.

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You can go and read up on the Internet about two, which complement

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to complement.

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Addition is a way for a computer to.

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Sure, negative numbers.

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OK, so he one show negative numbers.

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For example, here.

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When when you get on, once he refers to our.

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And then once the minister is a negative number, all right, so.

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That is the meaning of total premeditation, they are using binary numbers to represent sine integers.

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So when you have a negative number, you put negative.

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He put s in front.

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The most significant bit will be F or one.

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This is in your case, that is a negative number.

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If it's O F, then for sure is negative one.

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So no need to go too much.

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Just know that when you see all f he means negative one.

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So when you return negative one, you will return to the colony so you can step out of it.

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So here, if you return negative one, then you know that something that has gone wrong, something

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bad has happened in your Silkies from.

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So you can actually put a comment here to say that you the return value is negative one.

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He means wrong silkie.

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So is on this, you know, it is wrong here, OK, you can bring in this variable.

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OK, so just rename it now to return value on returning to you

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again, then here, if your return is zero, then put gutsier.

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So that is what we are seeing here.

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You see, that means we return to zero.

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All right, but if you return with a negative one, this would not be true.

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Instead, you ran this spot and put Vetsera before you.

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So zero a return radio zero means your your result is correct.

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Even return radio Ninety-One means exactly zero.

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So let's go back and see what makes it return.

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Zero changes.

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So over here, it returns you.

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Here it is, 81, so in here, the moment, the wrong city center city, we return 91.

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So if he doesn't return negative one, then he will continue to check all the remaining characters until

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he finishes.

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Once he finishes, he will look and come on here and return zero.

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So we know that this is the return that you see.

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This return is you you've won.

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So we can actually.

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Right.

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Click on this and give me a return integer.

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So when he return zero, it means you have successfully and technically right here.

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So when you return zero here and you go back out to function, the zero, the return here is zero again.

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When he comes here, he will return zero.

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Returning to zero, so this is true and he shows you the good message.

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So this is how to solve these crimes.

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That's all for this video.

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Thank you for watching.