Problem:
Score : 200 points

Problem Statement

Given are integers a,b,c and d.
If x and y are integers and a \leq x \leq b and c\leq y \leq d hold, what is the maximum possible value of x \times y?

Constraints

-10^9 \leq a \leq b \leq 10^9

-10^9 \leq c \leq d \leq 10^9

All values in input are integers.

Input

Input is given from Standard Input in the following format:

a b c d

Output

Print the answer.

Sample Input 1

1 2 1 1

Sample Output 1

2

If x = 1 and y = 1 then x \times y = 1.
If x = 2 and y = 1 then x \times y = 2.
Therefore, the answer is 2.

Sample Input 2

3 5 -4 -2

Sample Output 2

-6

The answer can be negative.

Sample Input 3

-1000000000 0 -1000000000 0

Sample Output 3

1000000000000000000

Solution in Rust (1.42.0) (judge verdict: Accepted)

fn main(){
    let v: Vec<isize> = read_vec();

    let vm: Vec<isize> = vec![v[0] * v[2], v[0] * v[3], v[1] * v[2], v[1] * v[3]];

    let ans = vm.iter().max().unwrap();

    println!("{}", ans)
}

#[allow(dead_code)]
fn read<T>() -> T
where T: std::str::FromStr,
      T::Err: std::fmt::Debug
{
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).expect("failed to read");
    buf.trim().parse().unwrap()
}

#[allow(dead_code)]
fn read_vec<T>() -> Vec<T>
where T: std::str::FromStr,
      T::Err: std::fmt::Debug
{
    let mut buf = String::new();
    std::io::stdin().read_line(&mut buf).expect("failed to read");
    buf.split_whitespace().map(|e| e.parse().unwrap()).collect()
}