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