Problem Statement

There is a farm whose length and width are $A$ yard and $B$ yard, respectively. A farmer, John, made a vertical road and a horizontal road inside the farm from one border to another, as shown below: (The gray part represents the roads.)

What is the area of this yard excluding the roads? Find it.

Note

It can be proved that the positions of the roads do not affect the area.

Constraints

• $A$ is an integer between $2$ and $100$ (inclusive).
• $B$ is an integer between $2$ and $100$ (inclusive).

Input

Input is given from Standard Input in the following format:

A B

Output

Print the area of this yard excluding the roads (in square yards).