Short story in the trurl's machine?

It's about an inventor named Trurl and he invented a thinking machine. Trurl always asks what two plus two is to the machine, and the machine always answered four. But one day the machine answered seven, and Trurl got really mad and said it was stupid. Then the machine tries to kill him and his friend, so they hide in a cave but eventually the machine dies. When it died Trurl said that two plus two was four at first, but then said seven.