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 C (GCC 9.2.1) (judge verdict: Wrong Answer)

#include <stdio.h>
int main(void)
{
  int a,b,c,d;
  scanf("%d %d %d %d", &a, &b, &c, &d);
  int ac = a * c;
  int ad = a * d;
  int bc = b * c;
  int bd = b * d;
  if (ac > ad)
  {
    if (ac > bc)
    {
      if (ac > bd)
      {
        printf("%d", ac);
      }
      else
      {
        printf("%d", bd);
      }
    }
    else
    {
      if (bc > bd)
      {
        printf("%d", bc);
      }
      else
      {
        printf("%d", bd);
      }
    }
  }
  else
  {
    if (ad > bc)
    {
      if (ad > bd)
      {
        printf("%d", ad);
      }
      else
      {
        printf("%d", bd);
      }
    }
    else
    {
      if (bc > bd)
      {
        printf("%d", bc);
      }
      else
      {
        printf("%d", bd);
      }
    }
  }
  return 0;
}