Problem:
Score : 100 points

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?

Constraints

2 ≤ n, m ≤ 100

Input

Input is given from Standard Input in the following format:

n m

Output

Print the number of blocks in K-city.

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:

Solution in OCaml (4.02.3) (judge verdict: Accepted)

let solve n m = (n - 1) * (m - 1)

let read_ints () = read_line () |> Str.split (Str.regexp " ") |> List.map int_of_string

let _ =
  match read_ints () with
  | [n; m] -> solve n m |> string_of_int |> print_endline
  | _ -> ()