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