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.

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).

Constraints

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

Sample Input 1

2 2

Sample Output 1

1

In this case, the area is 1 square yard.

Sample Input 2

5 7

Sample Output 2

24

In this case, the area is 24 square yards.

见题面 Input 部分

见题面 Output 部分