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); } } }