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;

class Program
{
    static void Main(string[] args)
    {
        string[] input = Console.ReadLine().Split(' ');
        long a = long.Parse(input[0]);
        long b = long.Parse(input[1]);
        long c = long.Parse(input[2]);
        long d = long.Parse(input[3]);

        long r = long.MinValue;

        long ac = a * c;
        long bc = b * c;
        long ad = a * d;
        long bd = b * d;

        r = ac;
        if (bc > r)
        {
            r = bc;
        }

        if (ad > r)
        {
            r = ad;
        }

        if (bd > r)
        {
            r = bd;
        }

        Console.WriteLine(r);
    }
}