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 PHP (7.4.4) (judge verdict: Accepted)

<?php 

$l = explode(" ", trim(fgets(STDIN)) );

$a = $l[0];
$b = $l[1];
$c = $l[2];
$d = $l[3];

$max = $a * $c;

if( $max < $a * $d ){
    $max =  $a * $d;
}
if( $max < $b * $c ){
    $max =  $b * $c;
}
if( $max < $b * $d ){
    $max =  $b * $d;
}

print $max;