#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  string s;
  cin >> n >> s;
  int b[200001] = {};
  int w[200001] = {};
  for (int i = 0; i < n; i++) {
    if (s[i] == '#')
      b[i + 1]++;
    else
      w[i + 1]++;
    b[i + 1] += b[i];
    w[i + 1] += w[i];
  }
  int ans = 1e9;
  if (b[n] == 0) {
    cout << 0 << endl;
    return 0;
  }
  for (int i = 0; i < n; i++) {
    if (s[i] == '#') {
      ans = min(ans, b[i] - b[0] + w[n] - w[i + 1]);
    }
  }
  cout << ans << endl;
  return 0;
}
