After using toilet water for so many years, you don't even know 90% of its usefulness!

Date:2018-09-19
窗户清洗
One night when I got home from work, a security guard came on patrol and suddenly shouted to me: Stop! What for?
I just got off work....
Security guard: What are the colors of CMYK?
Me: Cyan, magenta, yellow, black.
Security: You can go now.
I was surprised.
Me: Why do you ask such a question?
Security guard: I was still hanging around in the community late at night, looking bitter, either a thief or a designer.