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

class Program
{
    static void Main()
    {
        long[] n = Console.ReadLine().Split().Select(a => long.Parse(a)).ToArray();
        if(n[2] == 0)
        {
            Console.WriteLine($"{n[0]}");
            return;
        }
        if(n[2] == 1)
        {
            Console.WriteLine($"{n[1]}");
            return;
        }
        long before2 = n[0];
        long before1 = n[1];
        long current = before2 ^ before1;
        for(long i = 2; i < n[2]; i++)
        {
            before2 = before1;
            before1 = current;
            current = before2 ^ before1;
        }
        Console.WriteLine($"{current}");
    }
}