import java.util.Scanner;
public class No64 {

	public static void main(String[] args) {
		Scanner s = new Scanner(System.in);
		long f0 = s.nextLong() , f1 = s.nextLong() , N = s.nextLong();
		s.close();
		long f2 = f0 ^ f1;
		if(N % 3 == 0){
			System.out.println(f0);
		}else if(N % 3 ==1){
			System.out.println(f1);
		}else{
			System.out.println(f2);
		}

	}

}