#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  bool isS = false, isD = false;
  int r1 = 0, r2 = 0, r3 = 0;
  for (int i = n - 1; i >= 0; i--) {
    if (s.at(i) == '#') {
      r1++;
      isS = true;
      if (isD) r3++;
    } else if (isS) {
      r2++;
      isD = true;
    }
  }
  cout << min(r3, min(r1, r2)) << endl;
}
