package me.yukicoder.lv1_5;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class No0064 {
	public static void main(String[] args) {
		try (BufferedReader br = new BufferedReader(new InputStreamReader(System.in))) {
			String[] str = br.readLine().split(" ");
			long f0 = Long.parseLong(str[0]);
			long f1 = Long.parseLong(str[1]);
			long n = Long.parseLong(str[2]);

			System.out.println(xor(f1, f0, n));
		} catch (IOException e) {
			e.printStackTrace();
		}
	}

	static long xor(long f1, long f0, long n) {

		if (n == 0) {
			return f0;
		} else if (n == 1) {
			return f1;
		}

		long fk1 = f1;
		long fk2 = f0;
		long fk = fk1 ^ fk2;
		for (long i = 0; i < n - 2; i++) {
			fk2 = fk1;
			fk1 = fk;
			fk = fk1 ^ fk2;
		}
		return fk;
	}
}