package no064;

import java.util.Scanner;

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long[] f = new long[3];
		f[0] = sc.nextLong();
		f[1] = sc.nextLong();
		f[2] = f[0] ^ f[1];
		long n = sc.nextLong();
		System.out.println(f[(int) (n%3)]);
	}

}