#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  char a[200005];
  cin >> n;
  for (int i = 0; i < n; i++) {
    cin >> a[i];
  }
  int cnt = 0;
  for (int i = 1; i < n; i++) {
    if (a[i - 1] == '#' && a[i] == '.') {
      cnt++;
    }
  }
  cout << cnt;
  return 0;
}
