cf 978B

#include<bits\stdc++.h>

using namespace std;

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

    string s;
    cin >> s;

    int i, cnt = 0;
    for(i = 0; i < n - 2; i++)
    {
        if(s[i] == 'x' && s[i+1] == 'x' && s[i+2] == 'x') cnt++;
    }
    cout << cnt << endl;
}