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)

use proconio::input;
use std::cmp;

#[allow(unused_macros)]
macro_rules! multi_max {
    ( $a:expr, $b:expr ) => (std::cmp::max($a, $b));
    ( $a:expr, $b:expr, $($rest:expr),* ) => (std::cmp::max($a, multi_max![$b, $($rest),*]));
}

fn main() {
    input! {
        a: i64,
        b: i64,
        c: i64,
        d: i64,
    }

    let ans = multi_max!(a * c, a * d, b * c, b * d);
    println!("{}", ans);
}