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# (.NET Core 3.1.201) (judge verdict: Wrong Answer)

using System;
using System.Linq;
using System.Numerics;
namespace Sample
{
  class Sample
  {
    static void Main(string[] args)
    {
    string[] str=Console.ReadLine().Split(' ');
      BigInteger a=BigInteger.Parse(str[0]);
      BigInteger b=BigInteger.Parse(str[1]);
      BigInteger c=BigInteger.Parse(str[2]);
      BigInteger d=BigInteger.Parse(str[3]);
      BigInteger ans=0;
      if((b>=0)&&(d>=0)){
        ans=(b*d);
      }else if((a<0)&&(c<0)){
        ans=(a*c);
      }else if((a<0)&&(c>=0)){
        ans=(a*d);
      }else if((b>=0)&&(d<0)){
        ans=(a*d);
      }
         Console.WriteLine(ans);
    }
    
  }

}