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