A kangaroo kept getting out of his enclosure at the zoo. Knowing that he could hop pretty high, the zoo officials put up a ten-foot fence.
The next morning the kangaroo was out sauntering around the zoo again, so a twenty-foot fence was put up.
Again he got out, so they erected a fence 30 feet high.
The camel in the next pen asked the kangaroo, “How high do you think they’ll go?”
The kangaroo shrugged, “That all depends on how long it takes before somebody starts to lock the gate at night!”