One day, zoo keepers discovered that the kangaroos had escaped from their cages. After a meeting, they collectively concluded that the cage height was insufficient, so they decided to increase it from 10 meters to 20 meters. However, the next day, the kangaroos had escaped again, so the keepers decided to increase the height to 30 meters. To their surprise, the following day, all the kangaroos were out again. Panicking, the keepers decided to go all the way and increase the cage height to 100 meters. One day, while chatting, a giraffe asked the kangaroos, "Look, do you think these people will keep making your cages taller?" "Hard to say," a kangaroo replied, "If they keep forgetting to close the door!"
