There was a wooden bridge on top of a river in a city.
whenever people walked over it to cross the river,they would fall down.
To take care of this problem,the city appointed a strong policeman to stand under the bridge to save poeple who fall down.
while this helped the problem to some extent pople continued to fall down the bridge.
When the policeman moved to a different position,a new policeman was appointed to the job.
During the first few days,instead of standing at the botton of the bridge and saving the falling people,the new policeman worked with an engineer and fixed the hole on the bridge,which had not been noticed by the earlier policeman.
People the stopped falling down the bridge and the newe policeman did not have anyone to save.
This made his current job redundant and he moved on to do other things that yielded even better results for himself and the people.