import java.util.Scanner;

public class No64 {
	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 = F0 ^ F1;
		
		if(N % 3 == 0) {
			System.out.println(F0);
		}else if(N % 3 == 1) {
			System.out.println(F1);
		}else {
			System.out.println(Fn);
		}
	}
}