import java.util.Scanner;

public class Main{
	public static void main(String[] args){
		Scanner sc=new Scanner(System.in);
		while(sc.hasNext()){
			long f0=sc.nextLong();
			long f1=sc.nextLong();
			long f2=f0^f1;
			long n=sc.nextLong();
			if(n%3==0) System.out.println(f0);
			else if(n%3==1) System.out.println(f1);
			else System.out.println(f2);
		}
	}
}