import java.util.Scanner;
import java.util.ArrayList;
import java.util.Arrays;
import java.util.Collections;

class Main {
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        long[] f = new long[3];
        f[0] = in.nextLong();
        f[1] = in.nextLong();
        f[2] = f[0] ^ f[1];

        long n = in.nextLong();

        System.out.println(f[(int)(n%3)]);

        in.close();
    }
}