import java.util.Scanner;

public class Yukicoder64 {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long f0 = sc.nextLong();
		long f1 = sc.nextLong();
		long N = sc.nextLong();
		
		long fn;
		
		if (N % 3 == 0) fn = f0;
		else if (N % 3 == 1) fn = f1;
		else fn = f0 ^ f1;
		
		System.out.println(fn);
	}
}