import java.util.*;

public class ok{
	public static void main(String[] args) {
		Scanner sc=new Scanner (System.in);
		long f=sc.nextLong();
		long g=sc.nextLong();
		int n=sc.nextInt();
		long h=f^g;
		long ans;
		if(n%3==0)ans=f;
		else if(n%3==1)ans=g;
		else ans=h;
		
		System.out.println(ans);
	}}