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>
using namespace std;

#define ll long long

int main() {
    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    ll sz[4];
    sz[0] = a*c;
    sz[1] = a*d;
    sz[2] = b*c;
    sz[3] = b*d;
    ll M = sz[0];
    for(int i=1; i<4; i++) {
        M = max(M, sz[i]);
    }
    cout << M << endl;
    return 0;
}