I've got an old one, not really however focused on programming. <<A physicist, a computer scientist and a mathematician find themselves in prison. They all bra

I've got an old one, not really however focused on programming. <<A physicist, a computer scientist and a mathematician find themselves in prison. They all brag to each other that thanks to their superior knowledge, they will manage to escape relatively soon, and decide to bet they will be all out by one month. In the following month, the phyisicist gathers leftofers from meals, steals a few products from the janitors, and manages to assemble a corrosive substance that breaks the bars of his cell. He is out in 3 weeks. The computer scientist uses his weekly phonecalls to hack into the prison system, little by little. He manages to set the bars of his cell to open automatically right on the night of the 30th day, when he escapes. Out of his cell, he decides to go and check on his friends: the physicist is gone, instead the mathematician is dead in his cell in front of a long text on a wall which starts with "Proof: I will escape from prison. Reductio ad absurdum: let's assume I am already out of the prison...">>