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