#include <bits/stdc++.h>
using namespace std;
int main() {
  int N, cnt = 0;
  string S;
  cin >> N >> S;
  for (int i = 0; i < N; i++) {
    if (S[i] = '.') cnt++;
  }
  if (cnt == N) cnt = 0;
  if (cnt < (N / 2))
    cout << cnt << endl;
  else
    cout << N - cnt << endl;
}
