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>

#define MAX(A, B) ((A>B) ? A : B)
#define NUM 4
using namespace std;


int main(void){
    long long a, b, c, d;
    cin >> a >> b >> c >> d;
    
    long long ans_candidate[NUM] = {a*c, a*d, b*c, b*d};
    for(int i = 0; i < NUM-1; i++){
        ans_candidate[i+1] = MAX(ans_candidate[i], ans_candidate[i+1]);
    }
    cout << ans_candidate[NUM-1] << endl;
    
    return 0;
}