The question link is

Whenever I am initializing the variables (to store the sum of number of stamps and the sum of first N natural numbers) as long long, the verdict is WA. If I change to int, the verdict is AC.

The link of WA verdict:-

https://www.codechef.com/viewsolution/31763380

The link of AC verdict:-

https://www.codechef.com/viewsolution/31763291

Can anyone explain it??

1 Like

Your AC code fails on this test case

```
5
1000000000 1000000000 1000000000 1000000000 294967311
```

Tell me if you weren’t able to figure why it happens, and what is the correct answer.

Actually, I have initiated both sums as INT, but sum of these numbers cant be stored in INT.

When it overflows it almost always gives the same answer, so the chance of getting a test wrong is \approx 10^{-10}.

In the WA answer write

` long long int m=(long long)n*(n+1)/2;`

It overflows before it goes in `m`

.

I didn’t get the first line. Can you elaborate?

Overflow basically calculates the answer mod 2^{32}. The chance of 2 different numbers being equal mod 2^{32} is very low, that’s why your second solution got AC.