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