my logic is correct ,works properly for small numbers but I don’t what happens when input is 10^5…their is problem related to precision??

It is because of integer overflow, you have used int for storing n. Now, when answer(y) is calculated integer overflows.

```
y=((n+1)*(n+2))/2-1;
```

Solution : Just use long long for storing n. (or you can type cast n while calculating y )

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thank you for your support…