import java.util.Scanner;

public class Main64 {
	public static void main(String[] args) {
		Main64 p = new Main64();
	}

	public Main64() {
		Scanner sc = new Scanner(System.in);
		
		long f0 = sc.nextLong();
		long f1 = sc.nextLong();
		long n = sc.nextLong();
		solve(f0, f1, n);
	}

	public void solve(long f0, long f1, long n) {
		long res = 0;
		if(n%3==0)
			res = f0;
		else if(n%3==1)
			res = f1;
		else
			res = f0 ^ f1;
		
		System.out.println(res);
	}

}