package yukicoder064;
import java.util.Scanner;
public class Main {
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		long f0=sc.nextLong();
		long f1=sc.nextLong();
		long n=sc.nextLong();
		//00 0 00
		//01 1 01
		//10 1 10
		//11 0 11
		n=n%3;
		
		System.out.println(new long[]{f0,f1,f0^f1}[(int)n]);
	}
}