#include <bits/stdc++.h>
using namespace std;
int main() {
  int n, cnt = 0;
  string s;
  cin >> n >> s;
  for (int i = 0; i < n - 1; i++) {
    if ((s[i] == '#') && (s[i + 1] == '.')) {
      cnt++;
    }
  }
  cout << cnt << endl;
}
