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