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;
using System.Collections.Generic;

namespace ForAtcoder
{
    class Program
    {
        static void Main(string[] args)
        {
            var x = Console.ReadLine().Split(" ");
            var a = long.Parse(x[0]);
            var b = long.Parse(x[1]);
            var c = long.Parse(x[2]);
            var d = long.Parse(x[3]);

            if (a >= 0 && c >= 0 || b <= 0 && d <= 0)
            {
                if (a * c >= b * d) Console.WriteLine(a * c);
                else Console.WriteLine(b * d);
            }
            else if (b >= 0 && c <= 0 || d >= 0 && a <= 0)
            {
                if (a * d >= b * c) Console.WriteLine(a * d);
                else Console.WriteLine(b * c);
            }
            else
            {
                if (a * d >= b * c) Console.WriteLine(a * d);
                else Console.WriteLine(b * c);
            }

        }
    }
}