The funny joke in the exam is a jingle.

Two scholars failed in the science exam. On the way back, the more they thought about it, the more sad they became. Both of them felt full of knowledge, so they cried. At this moment, an old man who picked dung passed by them and asked, Why are you two crying so sad? Two people told Lao Zhang about it, and Lao Zhang said that since you are so talented, show it to me. The two men thought for a moment and decided to give Lao Zhang a pair. The first man walked out of the first part of the book and "saw the sawtooth on the wall in the distance". The second man took a close look at the wall saw and praised each other after reading it. At this time, they listened to Lao Zhang crying beside him, and they asked why. Lao Zhang said, unfortunately, it's a pity that you two are full of shit, and I can't get it out.