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 got out.
When the fence was forty feet high, a camel in the next enclosure asked the kangaroo,
How high do you think theyll go?
The kangaroo said, About a thousand feet, unless somebody locks the gate at night!