import java.util.*;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);
        long F0 = sc.nextLong();
        long F1 = sc.nextLong();
        long F2 = F0^F1;
        Long C = sc.nextLong();
        if(C%3==0){
            System.out.println(F0);
        }else if(C%3==1){
            System.out.println(F1);
        }else{
            System.out.println(F2);
        }
    }
}