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