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