using System;
using System.Collections;
using System.Collections.Generic;
using System.Collections.Specialized;
using System.Text;
using System.Text.RegularExpressions;
using System.Linq;

class Magatro
{
    static int N = int.Parse(Console.ReadLine());
    static string S = Console.ReadLine();

    static void Main()
    {
        if (N == 1) Console.WriteLine("NO");
        else if (N == 2)
        {
            if (S == "00" || S == "11") Console.WriteLine("YES");
            else Console.WriteLine("NO");
        }
        else if (N == 3)
        {
            if (S == "101" || S == "010") Console.WriteLine("NO");
            else Console.WriteLine("YES");
        }
        else Console.WriteLine("YES");
    }

}