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

class Program
{
    public static void Main(string[] args)
    {
        var line = Console.ReadLine().Split(' ').Select(ulong.Parse).ToArray();
        var f = new ulong[3];
        f[0] = line[0];
        f[1] = line[1];
        var n = line[2];
        f[2] = f[0] ^ f[1];
        Console.WriteLine(f[n%3]);
    }
}