A kangaroo kept getting out of his enclosure at the zoo.

After recapturing the kangaroo, the zookeeper put up a ten-foot fence. Again the kangaroo was out the next morning, roaming around the zoo. So the fence was extended to twenty feet. But again the kangaroo was out the next morning.

Frustrated zoo officials built a fence forty feet high.

A camel in the next enclosure asked the kangaroo, "How much higher do you think they'll go?"

The kangaroo said, "About a thousand feet I guess -- unless somebody starts locking the gate!"