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