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

namespace Test
{
    class Program
    {
        static void Main(string[] args)
        {
            long[] x = Console.ReadLine().Split().Select(long.Parse).ToArray();
            switch (x[2] % 3)
            {
                case (0):
                {
                    Console.WriteLine(x[0]);
                    break;
                }
                case (1):
                {
                    Console.WriteLine(x[1]);
                    break;
                }
                case (2):
                {
                    Console.WriteLine(x[0] ^ x[1]);
                    break;
                }
            }
        }
    }
}