import java.util.*;
 

public class Main {

	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		long n = sc.nextLong();
		long m=sc.nextLong();
		long l=sc.nextLong();
		long n2=n^m;
		if(l%3==0) System.out.println(n);
		else if(l%3==1) System.out.println(m);
		else System.out.println(n2);
	}
}