import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int n = sc.nextInt();
        char[] s = sc.next().toCharArray();

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

        System.out.println(num);
    }
}
