Here's my code,and I don't know what's wrong with it?
#include<iostream>
using namespace std;
char s[25];
int main()
{
    __int64 n,k;
    while(scanf("%I64d%s",&n,s)!=-1)
    {
        k=strlen(s);
        if(n<=k)
        {
            printf("%I64d\n",n);
        }
        else
        {
            __int64 sum=1,i;
            if(n%k==0)
            {
                for(i=n;i>=k;i-=k)
                    sum*=i;
            }
            else
            {
                for(i=n;i>=n%k;i--)
                    sum*=i;
            }
            printf("%I64d\n",sum);
        }
    }
    return 0;
}

Edited by author 15.06.2013 12:54

Edited by author 15.06.2013 12:56