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

namespace AtCoderBeginnerContest178
{
    class Program
    {
        static void Main(string[] args)
        {
            // 課題B - Product Max(2020/9/13)

            string[] input = Console.ReadLine().Split(' ');
            long max = -100000000000000000;
            long tmpResult;

            for(int i= 0; i<2; i++)
            {
                for(int j=2; j<4; j++)
                {
                    tmpResult = long.Parse(input[i]) * long.Parse(input[j]);
                    if (tmpResult > max) max = tmpResult;
                }
            }

            Console.Write(max);

        }
    }
}