#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, swp;
  char S[124];
  cin >> N >> S;
  for (int i = 0; i < N; i++)
    if (S[i] == '#' && S[i + 1] == '.') {
      S[i + 1] = '#';
      swp++;
    }
  cout << swp;
  return 0;
}
