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

class Program
{
    static void Main(string[] args)
    {
        var sol = new Solve();
        sol.Exec();
    }
}

class Solve
{
    public void Exec()
    {
        var ans = Console.ReadLine().Split().Select(int.Parse).ToArray();
        Array.Sort(ans);
        for (var i = 1; i < 4; i++)
        {
            if (ans[i] != ans[i - 1] + 1)
            {
                Console.WriteLine("No");
                return;
            }
        }

        Console.WriteLine("Yes");
    }
}

public class Util
{
}