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;
using System.Linq;

namespace B
{
	class Program
	{
		static void Main(string[] args)
		{
			var abcd = Console.ReadLine().Split(" ").Select(n => long.Parse(n)).ToArray();
			long a = abcd[0];
			long b = abcd[1];
			long c = abcd[2];
			long d = abcd[3];
			long max = long.MinValue;
			foreach (var ab in new long[] { a, b })
			{
				foreach (var cd in new long[] { c, d })
				{
					max = Math.Max(max, ab * cd);
				}
			}

			Console.WriteLine(max);
		}
	}
}