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++ (Clang 10.0.0) (judge verdict: Accepted)

#include <iostream>
using namespace std;

#define print(x) cout << #x << '=' << x << endl

int main()
{
    long long a,b,c,d,ans1,ans2,ans3,ans4;
    cin >> a >> b >> c >> d;

    ans1 = a*c;
    ans2 = a*d;
    ans3 = b*c;
    ans4 = b*d;

    cout << max(ans1,max(ans2,max(ans3,ans4))) << endl;
    return 0;
}