import java.io.*;
import java.util.*;

public class BinaryTreeTraversal {

    /**
     * @param args
     */
    public static void main(String[] args) {
        // TODO Auto-generated method stub
        new BinaryNode<Character>('x');
        Scanner input = new Scanner("input.txt");
        int n = input.nextInt();
        int m = (int) Math.pow(2,n)-1;
        BinaryNode<Character>[] array = new BinaryNode<Character>[m];

        //assigns to null
        for (Character c : input.nextLine().toCharArray()) {
            array[i] = new BinaryNode<Character>(Character.isLetter(c) ? c : null);
        }

        System.out.println(n);
    }
}