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

class TEST{
	static void Main(){
		Sol mySol =new Sol();
		mySol.Solve();
	}
}

class Sol{
	public void Solve(){
		
		String Ans="YES";
		switch(S){
			case "0":Ans="NO";break;
			case "1":Ans="NO";break;
			case "10":Ans="NO";break;
			case "01":Ans="NO";break;
			case "010":Ans="NO";break;
			case "101":Ans="NO";break;
			default:break;
		}
		Console.WriteLine(Ans);
	}
	int N;
	String S;
	public Sol(){
		N=ri();
		S=rs();
	}




	static String rs(){return Console.ReadLine();}
	static int ri(){return int.Parse(Console.ReadLine());}
	static long rl(){return long.Parse(Console.ReadLine());}
	static double rd(){return double.Parse(Console.ReadLine());}
	static String[] rsa(){return Console.ReadLine().Split(' ');}
	static int[] ria(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>int.Parse(e));}
	static long[] rla(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>long.Parse(e));}
	static double[] rda(){return Array.ConvertAll(Console.ReadLine().Split(' '),e=>double.Parse(e));}
}