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

namespace yukicoder_581 {
    class Program {
        static void Main(string[] args) {
            string[]s = Console.ReadLine().Split(' ');
            long a, b, c;
            a = long.Parse(s[0]);
            c = long.Parse(s[1]);
            b = a ^ c;
            Console.WriteLine(b);
            Console.ReadLine();
        }
    }
}