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)

#![allow(unused_imports)]
use proconio::marker::*;
use proconio::{fastout, input};
use std::cmp::max;

#[fastout]
fn main() {
    input! {
        a: isize,
        b: isize,
        c: isize,
        d: isize,
    }

    let res = solve(a, b, c, d);
    println!("{}", res);
}

fn solve(a: isize, b: isize, c: isize, d: isize) -> isize {
    let plus = b * d;
    let minus = a * c;
    let ab = a * d;
    let cd = c * b;
    max(plus, max(minus, max(ab, cd)))
}