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
#define ld long double
#define rep(i, n) for (ll i = 0; i < (ll)(n); i++)
#define Yes() std::cout << "Yes" << std::endl
#define No() std::cout << "No" << std::endl
#define Say(s) std::cout << s << std::endl
const ll MOD = 1000000007;
const ll INF = 1061109567;

int main()
{
    ll a, b, c, d;
    std::cin >> a >> b >> c >> d;
    ll max;
    max = c * a;
    max = std::max(max, a * d);
    max = std::max(max, b * d);
    max = std::max(max, b * c);
    Say(max);
    return 0;
}