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.Linq;

class Program
{
    static void Main()
    {
        var num = Console.ReadLine().Split(' ').Select(_ => long.Parse(_)).ToArray();
        long[] list = new long[4];
        list[0] = num[0] * num[2];//ac
        list[1] = num[0] * num[3];//ad
        list[2] = num[1] * num[2];//bc
        list[3] = num[1] * num[3];//bd

        long max = list.Max();
        Console.WriteLine((max));

    }
}