what is wrong?

#include <iostream>
#include <cmath>
#include <map>
#include <vector>
using namespace std;

int main()
{
    int n;
    string str;
    cin >> n >> str;

    int k = str.size();
    int i = 0;
    int sum = 1;
    if(n % k == 0)
    {
        while(i != n / k)
        {
            sum *= n - k * i;
            i++;
        }
    }
    else
    {
        while(i != n / k + 1)
        {
            sum *= n - k * i;
            i++;
        }
        sum *= n % k;
    }

    cout << sum << endl;

    return 0;
}

Edited by author 31.12.2015 12:38

It would be great if you stop searching telepathists and show error message.

Is it compilation error? Add "#include <string>" line.
Is it WA? Strange. Code looks working.
Is it any another error? Show it.

WA #10

Some people suppose n can be 20 so int is not enough for sum.
Try to use long long sum.

WA #10

Test:
5 !!!
answer 10, your answer 20

5!!!
here k=3,
5 isn't divisible by 3
so you have to multiply 5%3=2 with 5*(5-3)
so the answer is 5*2*2=20