Showing wrong answer, but I think that my solution is right

problem - Contest Page | CodeChef

my solution -
using namespace std;

int main() {
int n,sum=0;
cin >> n;
for(int i=1; i <= n; i++){
sum += i;
cout << sum;
return 0;

I tried custom input which gives right answer…but on submission it says wrong ans…
what am I doing wrong ?
please help…

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@ssjgz thanks , for telling me that…
I have edited the post…

I guess time complexity here is O(1), so you won’t be able to use a loop

there are two mistakes. first you should use long long data type instead of int. And instead of loop, use addition formula n*(n+1)/2. Loop may give TLE

@aamodpandey thanks…that worked.

@shubh_1664 yes, that was the problem… thanks

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