#include <bits/stdc++.h>
using namespace std;
int main() {
  int n;
  cin >> n;
  string s;
  cin >> s;
  vector<int> vec(n);
  vector<int> bec(n);
  if (s.at(0) == '#') {
    vec[0] = 1;
  } else {
    vec[0] = -1;
    bec[0] = 1;
  }
  for (int i = 1; i < n; i++) {
    if (s.at(i) == '#') {
      vec[i] += 1 + vec[i - 1];
      bec[i] = bec[i - 1];
    } else {
      vec[i] += vec[i - 1] - 1;
      bec[i] += 1 + bec[i - 1];
    }
  }
  if (vec[n - 1] == n) {
    cout << 0 << endl;
  } else {
    sort(vec.begin(), vec.end());
    cout << vec[0] + bec[n - 1] << endl;
  }
}
