cf A. Down the Hatch!

http://codeforces.com/contest/332/problem/A

 #include <cstdio>
 #include <iostream>
 #include <cstring>
 #include <algorithm>
 #define maxn 3000
 using namespace std;

 char str[maxn];

 int main()
 {
     int n;
     cin>>n;
     cin>>str;
     int k=strlen(str);
     int cnt=;
     for(int i=n; i<k; i+=n)
     {
         if(str[i-]==str[i-]&&str[i-]==str[i-])
             cnt++;
     }
     printf("%d\n",cnt);
     return ;
 }