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 io ios_base::sync_with_stdio(0);cin.tie(0);
#define mod 1000000009
#define pi 2*acos(0)
#define ll long long
#define ii pair<int,int>
#define vi vector<int>
using namespace std;


int main()
{

	io;
	
	ll a, b, c, d;
	cin >> a >> b >> c >> d;

	ll p1, p2, p3, p4;
	p1 = a * c; p2 = a * d; p3 = b * c; p4 = b * d;
	cout << max(p1, max(p2, max(p3, p4)));
}