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 Rust (1.15.1) (judge verdict: Accepted)

fn read() -> (i32, i32) {
    let mut s = String::new();
    std::io::stdin().read_line(&mut s).unwrap();
    let vec: Vec<i32> = s.split_whitespace().map(|x| x.parse().unwrap()).collect();
    (vec[0], vec[1])
}

fn main() {
    let (n, m) = read();
    println!("{}", (n - 1) * (m - 1))
}