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: Wrong Answer)

#include <bits/stdc++.h>
using namespace std;
typedef long long ll;
typedef pair<int, int> P;
// using cplx = complex<double>;

#define EPS (1e-7)
#define INF (1e9)
#define PI (acos(-1))
#define MAXN 1000010
#define rep(i, n) for(int i = 0; i < (n); ++i)
#define rep2(i, s, n) for(int i = (s); i < (int)(n); ++i)
const ll mod = 1e9 + 7;

template <class T>
inline bool chmax(T &a, T b) {
    if(a < b) {
        a = b;
        return 1;
    }
    return 0;
}
template <class T>
inline bool chmin(T &a, T b) {
    if(a > b) {
        a = b;
        return 1;
    }
    return 0;
}

bool pairCompare(const P &firstElof, const P &secondElof) {
    return firstElof.second < secondElof.second;
}

int main() {
    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    ll ans = pow(10, -18);
    ans = max(ans, a * c);
    ans = max(ans, a * d);
    ans = max(ans, b * c);
    ans = max(ans, b * d);
    cout << ans << endl;
}