import java.util.*;
import java.math.*;
import java.io.*;
 
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();
		if     (n % 3 == 0) System.out.println(f0);
		else if(n % 3 == 1) System.out.println(f1);
		else System.out.println(f0 ^ f1);
	}
}