#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;
  if (s[0] == '#') {
    for (int i = 0; i < n; ++i) {
      if (s[i] == '.') ++numw;
      if (s[i] == '#') ++numb;
    }
  } else {
    int repw = 0;
    for (int i = 0; i < n; ++i) {
      if (s[i] == '.')
        ++repw;
      else
        break;
    }
    for (int i = repw; i < n; ++i) {
      if (s[i] == '#') ++numw;
      if (s[i] == '.') ++numb;
    }
  }
  cout << min(numw, numb) << endl;
  return 0;
}
