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;
using System.Text;
using System.Threading.Tasks;

namespace AtCoder178
{
    class Program
    {
        static int[] RI()
        {
            return Console.ReadLine().Split(' ').Select(a => int.Parse(a)).ToArray();
        }

        static long[] RL()
        {
            return Console.ReadLine().Split(' ').Select(a => long.Parse(a)).ToArray();
        }

        static string RS()
        {
            return Console.ReadLine();
        }

        static void W(object msg)
        {
            Console.WriteLine(msg);
        }

        static void Main(string[] args)
        {
            QB();
        }

        static void QA()
        {
            W("0".Equals(RS()) ? "1" : "0");
        }

        static void QB()
        {
            long[] num = RL();

            long ac = num[0] * num[2];
            long ad = num[0] * num[3];
            long bc = num[1] * num[2];
            long bd = num[1] * num[3];

            W(Math.Max(Math.Max(ac, ad), Math.Max(bc, bd)));
        }

        static void QC()
        {

        }

        static void QD()
        {

        }

        static void QE()
        {

        }
    }
}