import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long[] value = new long[3];
        value[0] = sc.nextLong();
        value[1] = sc.nextLong();
        value[2] = value[0] ^ value[1];
        long n = sc.nextLong();
        System.out.println(value[(int)(n % 3)]);
    }
}