Problem:
﻿Score: 100 points

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).

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.

Solution in Rust (1.15.1) (judge verdict: Accepted)

#![allow(unused)]

use std::{cell, cmp, collections, fmt, ops};

use cell::{Cell, RefCell};
use cmp::Ordering::{Equal, Greater, Less};
use collections::{BTreeMap, BTreeSet, BinaryHeap, HashMap, HashSet, LinkedList, VecDeque};
use fmt::{Debug, Display};

#[cfg(feature = "debug")]
macro_rules! debug {
    ($($args: tt)*) => { eprint!($($args)*) };
}

#[cfg(feature = "debug")]
macro_rules! debugln {
    ($($args: tt)*) => { eprintln!($($args)*) };
}

#[cfg(not(feature = "debug"))]
macro_rules! debug {
    ($($args:tt)*) => {};
}

#[cfg(not(feature = "debug"))]
macro_rules! debugln {
    ($($args:tt)*) => {};
}

macro_rules! vmin {
    ($x: expr, $y: expr) => { cmp::min($x, $y) };
    ($x: expr, $($args: expr),*) => { cmp::min($x, vmin!($($args),*)) };
}

macro_rules! vmax {
    ($x: expr, $y: expr) => { cmp::max($x, $y) };
    ($x: expr, $($args: expr),*) => { cmp::max($x, vmax!($($args),*)) };
}

fn main() {
    use io::*;

    let ab = parse_vec::<i32>();
    let ans = (ab[0] - 1) * (ab[1] - 1);

    println!("{}", ans);
}

#[cfg(test)]
mod tests {
    use super::*;

    #[test]
    fn test() {
        //
    }
}

mod io {
    use std::io::{self, Read, Write};
    use std::str;

    pub fn read_line() -> String {
        let mut buf = String::new();
        io::stdin().read_line(&mut buf).unwrap();
        buf.trim().to_owned()
    }

    pub fn read_word() -> String {
        const CAPACITY: usize = 16;

        let mut stdin = io::stdin();
        let mut byte: [u8; 1] = [0];

        loop {
            let mut buf = Vec::with_capacity(CAPACITY);

            loop {
                let res = stdin.read(&mut byte);

                if res.unwrap_or(0) == 0 || byte[0] <= b' ' {
                    break;
                } else {
                    buf.push(byte[0]);
                }
            }

            if !buf.is_empty() {
                return String::from_utf8(buf).unwrap();
            }
        }
    }

    pub fn parse_line<T: str::FromStr>() -> T {
        read_line().parse().ok().unwrap()
    }

    pub fn parse_word<T: str::FromStr>() -> T {
        read_word().parse().ok().unwrap()
    }

    pub fn parse_vec<T: str::FromStr>() -> Vec<T> {
        read_line()
            .split_whitespace()
            .map(|e| e.parse().ok().unwrap())
            .collect()
    }

    pub fn flush() {
        io::stdout().flush();
    }
}

mod num {
    use std::{cmp, ops};

    pub fn imin<T, I>(v: &T) -> &I
    where
        T: ops::Deref<Target = [I]>,
        I: cmp::Ord + Copy,
    {
        v.iter().min().unwrap()
    }

    pub fn imax<T, I>(v: &T) -> &I
    where
        T: ops::Deref<Target = [I]>,
        I: cmp::Ord + Copy,
    {
        v.iter().max().unwrap()
    }

    pub fn next_prime(x: i32) -> i32 {
        for i in (x + 1).. {
            if is_prime(i) {
                return i;
            }
        }

        panic!("attempt to add with overflow");
    }

    pub fn is_prime(x: i32) -> bool {
        let ceil = f64::from(x).sqrt().ceil() as i32;
        x == 2 || (2..(ceil + 1)).all(|i| x % i != 0)
    }
}

mod bits {
    pub fn bit_high(bits: u64, pos: u64) -> bool {
        bits & (1 << pos) != 0
    }
}