是这样的，在昨天 ABC G 的题解介绍半群（好像也叫半环来着）的部分中，举了俩半群 $(A,+,\cdot)$ 的例子：

• For a positive integer $n$, $A$ is a set of non-negative integer less than $2 ^n$, $+$ is bitwise logical sum, and $\cdot$ is bitwise logical product.
• For a positive integer $n$, A is a set of non-negative integer less than $2^n$, $+$ is bitwise exclusive logical sum, and $\cdot$ is bitwise logical product.

谁知道这些 bitwise 操作符都是啥啊/kel

百度和必应无果。