On the day of graduation, I deleted all his contact information, thinking that I had completely cut off my youthful past.
Ten years later, at a class reunion, a worn out old notebook appeared
When I opened it, it turned out to be a collection of wrong math questions from my three years of high school, with new handwriting added next to each red pen annotation.
"The thirty-sixth review, I finally understand it completely. It's a pity that I can't tell you in person."
There was a note on the last page: "Actually, I was waiting for you to ask me the wrong question back then."
