#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  string S;
  cin >> N >> S;
  int count = 0;
  bool flag = false;
  for (int i = 0; i < N; i++) {
    if (S[i] == '#') {
      flag = true;
    } else if (flag) {
      count++;
    }
  }
  cout << count << endl;
}
