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: Wrong Answer)

<?php


$input_array = explode(" ", fgets(STDIN));

$ans = -1 * pow(10,-18);

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

$x_array = array($a, $b);
if ($a < 0 and $b > 0) {
    $x_array[] = 0;
}

$y_array = array($c, $d);
if ($c < 0 and $d > 0) {
    $y_array[] = 0;
}

foreach ($x_array as $x) {
    foreach ($y_array as $y) {
        if($x * $y > $ans){
            $ans = $x * $y;
        }
    }
}

echo $ans;

?>