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 <vector>
#include <limits.h>
#include <cmath>
using namespace std;
int main(void){
    // Your code here!
    long x1,x2,y1,y2;
    cin>>x1>>x2>>y1>>y2;
    long answer=-1*pow(10,18);
    vector<vector<long>> vec={{x1,x2},{y1,y2}};
    for(int i=0;i<2;i++){
        for(int j=0;j<2;j++){
            if(vec[0][i]*vec[1][j]>answer){
                answer=vec[0][i]*vec[1][j];
            }
        }
    }
    cout<<answer;
}