import java.util.Scanner;

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