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 repi(i, a, b) for (int i = (int)(a) ; i < (int)(b) ; i++)
#define rep(i, n) repi(i, 0, n)
#define SZ(x) ((int)(x).size())
typedef long long ll;
typedef unsigned long long ull;
typedef unsigned int uint;
// using P = pair<int, int>;
struct Vec{
    double x, y;
};
template<class T> inline bool chmin(T& a, T b) {
    if (a > b) {
        a = b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T& a, T b) {
    if (a < b) {
        a = b;
        return true;
    }
     return false;
}
using namespace std;
int main()
{
    cin.tie(nullptr);
    ios_base::sync_with_stdio(false);
    // cout << fixed << setprecision(15);
    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    cout << max(max(a*c, a*d), max(b*c, b*d)) << endl;
    return 0;
}