Albert Camilo, a famous expert in mental arithmetic, has never missed it.

On this day, he was performing, and someone came to the stage and gave him a question: "A train with 283 passengers entered the station, 87 people got off and 65 people got on; At the next stop, 49 people will go down and 1 12 people will come up; At the next stop, 37 people go down and 96 people come up; At the next stop, 74 people went down and 69 people came up; Once again, 17 people went down again, and 23 people came up ... "

No sooner had the man finished than the mental arithmetic master replied disdainfully, "Pediatrics! Tell you, this car and-"

"No," the man stopped him and said, "I asked you to count how many stops the train stopped."

Abbott Camilo was stunned, and this simple addition and subtraction became his "Waterloo".