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