#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] == '.') {
      int l = 1, r = 1;
      while (l >= 0 && s[i - l] == '#') ++l;
      while (r < n && s[i + 1 + r] == '.') ++r;
      answer += min(l, r);
      i += r;
    }
  }
  cout << answer << endl;
}
