#include <bits/stdc++.h>
using namespace std;
string s;
int n, res, t;
int main() {
  cin >> n >> s;
  for (int i = 0; i < n; ++i) {
    if (s[i] == 'x')
      ++t;
    else
      t = 0;
    if (t >= 3) ++res;
  }
  cout << res << endl;
  return 0;
}
