A kangaroo kept getting out of his enclosure at the zoo.
Knowing that he could hop high, the zoo officials put up a ten-
foot fence. He was out the next morning, just roaming around
the zoo. A twenty-foot fence was put up. Again he go out.
When the fence was forty feet high, a camel in the next
enclosure asked the kangaroo, "How high do you think they'll
go?"

The kangaroo said, "About a thousand feet, unless somebody
locks the gate at night!"