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
define("MOD", 10**9+7);

//$x = (int)trim(fgets(STDIN));
//$T = trim(fgets(STDIN));
list($a,$b,$c,$d) = array_map('intval',explode(" ",trim(fgets(STDIN))));
//$A = array_map('intval',explode(" ",trim(fgets(STDIN))));

$maxx = max($a,$b);
$maxy = max($c,$d);

if (($maxx < 0) && ($maxy > 0)) {
  $maxy = min($c,$d);
}
if (($maxx > 0) && ($maxy < 0)) {
  $maxx = min($a,$b);
}
if (($maxx < 0 && $maxy < 0)) {
  $maxx = min($a,$b);
  $maxy = min($c,$d);
}
if ($a==0) $maxx = $b;
if ($b==0) $maxx = $a;
if ($c==0) $maxy = $d;
if ($d==0) $maxy = $c;
printf("%d\n",$maxx*$maxy);