There's an old joke about a cop who's walking his beat in the middle of the night, and he comes across a guy under a street lamp who's looking at the ground and moving from side to side, and the cop asks him what he's doing.
有一个很古老的笑话， 一个警察在深夜里巡逻时 在路灯下遇到了一个男人 他一边盯着地面看一边来回走 警察问他在做什么