Score : $100$ points

问题陈述

给定两个在 $0$ 到 $255$（包含）之间的整数 $A$ 和 $B$。求一个非负整数 $C$，使得 $A \text{ xor } C = B$。

可以证明这样的 $C$ 存在且唯一，并且它也会在 $0$ 到 $255$（包含）之间。

什么是按位异或？

整数 $A$ 和 $B$ 的按位异或（$\mathrm{XOR}$），记作 $A\ \mathrm{XOR}\ B$，定义如下：

• 当以二进制形式表示 $A\ \mathrm{XOR}\ B$ 时，第 $2^k$ 位（$k \geq 0$）上的数字是：如果 $A$ 和 $B$ 中恰好有一个为 $1$，则该位为 $1$；否则为 $0$。

例如，我们有 $3\ \mathrm{XOR}\ 5 = 6$（以二进制表示：$011\ \mathrm{XOR}\ 101 = 110$）。

以上为通义千问 qwen-max 翻译，仅供参考。

Problem Statement

You are given integers $A$ and $B$ between $0$ and $255$ (inclusive). Find a non-negative integer $C$ such that $A \text{ xor }C=B$.

It can be proved that there uniquely exists such $C$, and it will be between $0$ and $255$ (inclusive).

What is bitwise $\mathrm{XOR}$?

The bitwise $\mathrm{XOR}$ of integers $A$ and $B$, $A\ \mathrm{XOR}\ B$, is defined as follows:

• When $A\ \mathrm{XOR}\ B$ is written in base two, the digit in the $2^k$'s place ($k \geq 0$) is $1$ if exactly one of $A$ and $B$ is $1$, and $0$ otherwise.

For example, we have $3\ \mathrm{XOR}\ 5 = 6$ (in base two: $011\ \mathrm{XOR}\ 101 = 110$).

Constraints

• $0\leq A,B \leq 255$
• All values in input are integers.

Input

Input is given from Standard Input in the following format:

$A$ $B$

Output

Print the answer.

Sample Input 1

3 6

Sample Output 1

5

When written in binary, $3$ will be $11$, and $5$ will be $101$. Thus, their $\text{xor}$ will be $110$ in binary, or $6$ in decimal.

In short, $3 \text{ xor } 5 = 6$, so the answer is $5$.

Sample Input 2

10 12

Sample Output 2

6

update @ 2024/3/10 09:29:04