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 sauntering around the zoo.

A twenty-foot fence was put up. Again he got 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 I guess... Or until someone notices the open gate."