import java.util.*;

public class Yukicoder_64{
	public static void main(String[] args){
		Scanner stdIn = new Scanner(System.in);
		long F0 = stdIn.nextLong();
		long F1 = stdIn.nextLong();
		long N = stdIn.nextLong();
		long count = N%(long)3;
		long F2 = F0^F1;
		if(count == 0){
			System.out.println(F0);
		}
		else if(count == 1){
			System.out.println(F1);
		}
		else if(count == 2){
			System.out.println(F2);
		}
	}
}