#include <bits/stdc++.h>
using namespace std;
const int INF = 1e9;
int main() {
  int n;
  string s;
  cin >> n >> s;
  int ans = 0;
  for (int i = 0; i < n - 1; i++) {
    if (s[i] == '#' && s[i + 1] == '.') {
      ans++;
    }
  }
  cout << ans << endl;
  return 0;
}
