#include <bits/stdc++.h>
using namespace std;
int main() {
  ios::sync_with_stdio(false);
  cin.tie(0);
  int n;
  cin >> n;
  string s;
  cin >> s;
  int numw, numb;
  numw = numb = 0;
  for (int i = 0; i < n; ++i) {
    if (s[i] == '.') ++numw;
    if (s[i] == '#') ++numb;
  }
  cout << min(numw, numb) << endl;
  return 0;
}
