A man sees in the street two workers performing the following procedure: The first one is digging a ditch, and the second one, a few feet behind is covering the ditch with the the sand that was just dug out.

After watching them for a while he could not resist his curiosity and he went to ask them what they are doing and what was the goal in their work.

"This is very simple, mister" said one of the workers. "Usually we are a team of three: One digs, the other puts communication cable into the ditch and the third one covers it. Unfortunately, the guy who puts the cables into the ditch is sick today, so we are doing the best we can."