import java.util.Scanner;

public class Test {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);

		long a = sc.nextLong(), b = sc.nextLong(), c = a^b, n = sc.nextLong();
		if(n%3 == 0){
			System.out.println(a);
		} else if(n%3 == 1){
			System.out.println(b);
		} else {
			System.out.println(c);
		}
	}
}