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)

mod io{
    use std::io::*;
    pub fn read<T: ::std::str::FromStr>()->T{
        let stdin=stdin();
        let ret=stdin.lock().bytes().map(|c|c.unwrap()as char)
        .skip_while(|c|c.is_whitespace())
        .take_while(|c|!c.is_whitespace())
        .collect::<String>().parse().ok().unwrap();
        ret
    }
}
use io::read;
fn main(){
    let a=read::<i32>();
    let b=read::<i32>();
    println!("{}",(a-1)*(b-1))
}