Jokes about negative numbers

Mathematicians, biologists and physicists sit in street cafes and watch people go in and out of the house across the street.

They saw two men go in first. As time went on, they saw three more people coming out.

Physicist: "The measurement is not accurate enough."

Biologist: "They reproduce."

Mathematician: "If one more person goes in now, the house will be empty."

It means: pure mathematical algorithm, two people go in and three people come out, which is negative. At this time, one more person will be zero.