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: Runtime Error)

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

class ProductMax
{


    static void Main(string[] args)
    {

        string[] input = Console.ReadLine().Split(" ");
        int a = int.Parse(input[0]);
        int b = int.Parse(input[1]);
        int c = int.Parse(input[2]);
        int d = int.Parse(input[3]);

        int[] xAry = Enumerable.Range(a, b).ToArray();
        int[] yAry = Enumerable.Range(c, d).ToArray();
        int[] answerAry = { };


        for (int i = 0; i <= xAry.Length; i++)
        {
            for (int r = 0; i <= yAry.Length; i++)
            {
                int answer = xAry[i] * yAry[r];
                Array.Resize(ref answerAry, answerAry.Length + 1);
                answerAry[answerAry.Length - 1] = answer;
            }

            Console.WriteLine(answerAry.Max());

        }
    }
}