using System;

namespace No64_XORFibonacciSequence
{
    internal class Program
    {
        static void Main(string[] args) {
            string[] param = Console.ReadLine().Split(' ');
            long f0 = long.Parse(param[0]);
            long f1 = long.Parse(param[1]);
            long n = long.Parse(param[2]);

            long result = 0;
            switch (n % 3) {
                case 0:
                    result = f0;
                    break;
                case 1:
                    result = f1;
                    break;
                case 2:
                    result = f1 ^ f0;
                    break;
            }
            Console.WriteLine(result);
        }
    }
}