using System;
public class Hello{
    public static void Main(){
       
        string[] inpt = Console.ReadLine().Split();
        var n = Array.ConvertAll(inpt, int.Parse);
        Array.Sort(n);
        
        for(int i=0;i<3;i++){
            if(n[i]!=n[i+1]-1){
                Console.WriteLine("No");
                return;
            }
        }
        
        
        Console.WriteLine("Yes");
        
    }
}