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: Accepted)

using System;
using System.Collections.Generic;
using System.Text;

namespace AtCoder
{
  class Program
  {
    static void Main(string[] args)
    {
      string[] ss = Console.ReadLine().Split(' ');
      long a = long.Parse(ss[0]);
      long b = long.Parse(ss[1]);
      long c = long.Parse(ss[2]);
      long d = long.Parse(ss[3]);
      Console.WriteLine(Math.Max(Math.Max(a * c, b * d), Math.Max(a * d, b * c)));
      Console.ReadLine();
    }

  }
}