There was a farmer who grew watermelons - Joke

There was a farmer who grew watermelons. He was doing
pretty well, but he was disturbed by some local kids who
would sneak into his watermelon patch at night and eat his
watermelons. After some careful thought, he came up with a
clever idea that he thought would scare the kids away for
sure.
He made up a sign and posted it in the field. The next
night, the kids showed up and they saw the sign which
read, "Warning! One of the watermelons in this field has
been injected with cyanide."
The kids ran off, made up their own sign and posted it next
to the farmer's sign. When the farmer returned, he surveyed
the field. He noticed that no watermelons were missing, but
the sign next to his read, "Now there are two!"