#include <iostream>
#include <string>
using namespace std;

int main(){
  int n;
  int count = 0;
  string s;

  cin >> n >> s;

  for(int i = 0;i < n;i++){
    if(s[i] == '#' && s[i+1] == '.' && i != n-1){
      if(s[i-1] == '.' && i != 0){
        count++;
        s[i] = ".";
      }
      else{
        count++;
        s[i+1] = '#';
      }
    }
  }

  cout << count << endl;

  return 0;
}
