#include <bits/stdc++.h>
using namespace std;
const int INF = 100100100;
const long long LINF = 1e18 + 100;
const int MOD = 1e9 + 7;
int main() {
  cin.tie(0);
  ios::sync_with_stdio(false);
  ;
  int N;
  string S;
  cin >> N >> S;
  long long ans = 0;
  bool on = false;
  for (int i = 0; i < (N); i++) {
    if (S[i] == '#') on = true;
    if (S[i] == '.' && on) ans++;
  }
  if (ans > N / 2) ans = N - ans;
  cout << ans << endl;
}
