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