using System;
using System.Linq;

class Program
{
    static void Main()
    {
        long[] l = Console.ReadLine().Split().Select(long.Parse).ToArray();
        long n = l[2];

        long[] f = new long[3];
        f[0] = l[0];
        f[1] = l[1];
        f[2] = f[0] ^ f[1];

        Console.WriteLine(f[n % 3]);       
    }
}