import java.util.Scanner;


public class Main_yukicoder64 {

    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        long[] f = new long[3];
        f[0] = sc.nextLong();
        f[1] = sc.nextLong();
        f[2] = f[0] ^ f[1];
        long n = sc.nextLong();
        
        System.out.println(f[(int)(n % 3)]);
        
        sc.close();
    }
}