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

namespace yukicoderTest
{
    class Program
    {
        static void Main(string[] args)
        {
            string[] input = Console.ReadLine().Split(' ');
            long a = long.Parse(input[0]);
            long c = long.Parse(input[1]);
            long ans = a ^ c;
            Console.WriteLine(ans);
        }
    }
}