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