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<bits/stdc++.h>
#define ll long long

using namespace std;

struct Node
{
    int data;
    struct Node* left;
    struct Node* right;
    Node(int x)
    {
        data=x;
        left=NULL;
        right=NULL;
    }
};
#define Node struct Node

int main()
{
    int t=1;
    //cin>>t;
    while(t--)
    {
        ll a,b,c,d;
        cin>>a>>b>>c>>d;
        cout<<max(a*c,max(a*d,max(b*c,b*d)))<<endl;
    }
    return 0;
}