Mr Smith liked to be exact（确切的）.One day when he was walking in the street，a man came over and asked him：
"Excuse me，but where's the nearest bookshop？"
"The nearest bookshop？You have to cross a bridge and then turn to the right.""And is the bridge long？"
"Very. Thirty metres.
The man thanked him and went towards the bridge. Suddenly he heard someone running after him.
"Stop!"Mr Smith was shouting, "I'm sorry. I just remembered, the bridge is forty metres long. If you go thirty metres and then turn to the right, as I told you to do just now, you' ll fall into the river.