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=0;
    for(int i=n; i<k; i+=n)
    {
        if(str[i-1]==str[i-2]&&str[i-3]==str[i-2])
            cnt++;
    }
    printf("%d\n",cnt);
    return 0;
}