Score : $100$ points
In K-city, there are $n$ streets running east-west, and $m$ streets running north-south. Each street running east-west and each street running north-south cross each other. We will call the smallest area that is surrounded by four streets a block. How many blocks there are in K-city?
Input is given from Standard Input in the following format:
Print the number of blocks in K-city.
There are six blocks, as shown below:
There are one block, as shown below: