One day, the staff at a zoo held a meeting to address an issue: kangaroos were escaping from their cage. They concluded the cage was too low and decided to raise it from one meter to two meters high.
The next day, the kangaroos were still at large. The staff raised the cage again, this time to three meters.
To their surprise, the kangaroos were free again the following morning. Alarmed, they determined to go to all lengths and raised the cage to ten meters.
Later, a giraffe chatted with some kangaroos. "Do you think they will keep raising your cage?" it asked.
"Hard to say," replied a kangaroo. "If they continue forgetting to fasten the cage door."