#include <bits/stdc++.h>
using namespace std;
int main() {
  int N;
  string S;
  cin >> N >> S;
  int cnt = 0;
  for (int i = 0; i < N - 1; i++) {
    if (S[i] == '#' and S[i + 1] == '.') cnt++;
  }
  cout << cnt << endl;
}
