import java.io.OutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.PrintWriter;
import java.util.Scanner;

/**
 * Built using CHelper plug-in
 * Actual solution is at the top
 */
public class Main {
    public static void main(String[] args) {
        InputStream inputStream = System.in;
        OutputStream outputStream = System.out;
        Scanner in = new Scanner(inputStream);
        PrintWriter out = new PrintWriter(outputStream);
        C solver = new C();
        solver.solve(1, in, out);
        out.close();
    }

    static class C {
        public void solve(int testNumber, Scanner in, PrintWriter out) {
            int N = in.nextInt();
            String S = in.next();
            char[] cs = S.toCharArray();

            boolean f = false;
            int count1 = 0;
            for (int i = 0; i < N; i++) {
                if (cs[i] == '#') {
                    f = true;
                } else if (f) {
                    count1++;
                }
            }
            f = false;
            int count2 = 0;
            for (int i = N - 1; i >= 0; i--) {
                if (cs[i] != '#') {
                    f = true;
                } else if (f) {
                    count2++;
                }
            }
            out.println(Math.min(count1, count2));
        }

    }
}

