#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  cin >> N;
  string S1;
  cin >> S1;
  string S2(S1.c_str(), S1.length());
  int ret1 = 0;
  for (int i = 0; i < N - 1; i++) {
    if (S1[i] == '#' && S1[i + 1] == '.') {
      S1[i + 1] = '#';
      ret1++;
    }
  }
  int ret2 = 0;
  for (int i = N - 1; i > 0; i--) {
    if (S2[i] == '.' && S2[i - 1] == '#') {
      S2[i - 1] = '.';
      ret2++;
    }
  }
  cout << min(ret1, ret2) << endl;
}
