Tell a joke, get a free rescue - Prize for the best joke and the worst joke too;)

Two madmen plan the escape of the maniconio, one says to the other:

• If the wall is low, we skip it, if it's high, we dig a hole, ¿Understood?
• Yes, - you can go first.
  After three hours the madman returns and says:
• We can not escape.
• Why?
• Because there's no wall!