#include <bits/stdc++.h>
using namespace std;
int N;
string S;
int main() {
  cin >> N >> S;
  int white = 0;
  for (int i = 0; i < N; i++) {
    if (S[i] == '.') white++;
  }
  int left_w = 0;
  for (int i = 0; i < N; i++) {
    if (S[i] == '.')
      left_w++;
    else
      break;
  }
  int black = 0;
  for (int i = 0; i < N; i++) {
    if (S[i] == '#') black++;
  }
  int right_b = 0;
  for (int i = 0; i < N; i++) {
    if (S[N - 1 - i] == '#')
      right_b++;
    else
      break;
  }
  int left_b = 0;
  for (int i = 0; i < N; i++) {
    if (S[i] == '#')
      left_b++;
    else
      break;
  }
  int right_w = 0;
  for (int i = 0; i < N; i++) {
    if (S[N - 1 - i] == '.')
      right_w++;
    else
      break;
  }
  int ans = min(white - left_w, min(black - right_b, left_b + right_w));
  cout << ans << endl;
}
