import java.util.*;
import static java.lang.System.*;

public class Main {
	static Scanner sc = new Scanner(System.in);
	public static void main(String[] args) {
		long F0 = sc.nextLong();
		long F1 = sc.nextLong();
		long n = sc.nextLong();
		long F2 = F0^F1;
		long ans;
		if(n%3==0)ans=F0;
		else if (n%3==1)ans=F1;
		else ans=F2;
		out.println(ans);
		
	}
}