Problem Statement

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

Input is given from Standard Input in the following format:
n m

Output

Print the number of blocks in K-city.

Constraints

• 2 ≤ n, m ≤ 100

Sample Input 1

3 4

Sample Output 1

6

There are six blocks, as shown below:

Sample Input 2

2 2

Sample Output 2

1

There are one block, as shown below:

见题面 Input 部分

见题面 Output 部分