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