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