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++ (GCC 9.2.1) (judge verdict: Accepted)

#include <iostream>
#include <algorithm>
#include <vector>
#include <cmath>
#include <set>

using namespace std;
const double PI(acos(-1));

int main()
{
    long long int A, B, C, D;
    cin >> A >> B >> C >> D;

    long long int s[4] = {};
    s[0] = A * C;
    s[1] = A * D;
    s[2] = B * C;
    s[3] = B * D;

    long long max = s[0];
    for (int i = 1; i < 4; i++)
    {
        if (s[i] > max)
        {
            max = s[i];
        }
    }

    cout << max;
}