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# (Mono-mcs 6.8.0.105) (judge verdict: Accepted)

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

namespace CSharpSample01
{
	class Program
	{
		static void Main(string[] args)
		{
			var inputNum = Console.ReadLine().Split(' ').Select(long.Parse).ToArray();

			var a = inputNum[0];
			var b = inputNum[1];
			var c = inputNum[2];
			var d = inputNum[3];

			long[] answerArray = new long[4];


			answerArray[0] = a * c;
			answerArray[1] = a * d;
			answerArray[2] = b * c;
			answerArray[3] = b * d;

			long answer = answerArray.Max();
			Console.WriteLine(answer);

		}

	}
}