using System;
using System.Linq;
class Program {
    static void Main() {
        long[] r = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();
        long[] f = new long[3];
        f[0] = r[0];
        f[1] = r[1];
        f[2] = f[0] ^ f[1];
        Console.WriteLine(f[r[2] % 3]);
    }
}