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.Collections.Generic;
using System.Linq;
using System;

public class Hello
{
    public static long a, b, c, d;
    public static void Main()
    {
        string[] line = Console.ReadLine().Trim().Split(' ');
        a = long.Parse(line[0]);
        b = long.Parse(line[1]);
        c = long.Parse(line[2]);
        d = long.Parse(line[3]);
        getAns();
    }
    static void getAns()
    {
        var ans = new List<long>();
        ans.Add(a * c);
        ans.Add(a * d);
        ans.Add(b * c);
        ans.Add(b * d);
        Console.WriteLine(ans.Max());
    }
}