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