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

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

            if (b > 0 && d > 0)
                Console.WriteLine(b * d);
            else if (b <= 0 && d <= 0)
                Console.WriteLine(a * c);
            else
            {
                var ab = b > 0 ? Math.Min(a, b) : Math.Max(a, b);
                var cd = d > 0 ? Math.Min(c, d) : Math.Max(c, d);
                Console.WriteLine(ab * cd);
            }
        }
    }
}