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>
using namespace std;
using ll = long long;
#define FASTIO ios::sync_with_stdio(false); cin.tie(nullptr)
#define rep(i, n) for(int (i) = 0; (i) < (int)(n); ++(i))
#define pb push_back
#define eb emplace_back
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())

int main() {
	FASTIO;
	ll a, b, c, d, ans = -1000000000000000000;
	cin >> a >> b >> c >> d;
    ans = max(max(a*c, a*d), max(b*c, b*d));
	cout << ans << endl;
}