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