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++ (Clang 10.0.0) (judge verdict: Accepted)

#include<iostream>
#include<vector>
#include <algorithm>
using namespace std;
using ll=long long;

#define loop(var,start,stop,step) for(long long var=start;var<stop;var+=step)

using vi=vector<int>;
using vl=vector<long long>;

#define fio  cin.tie(nullptr); ios::sync_with_stdio(false); cout.tie(nullptr);
#define nl cout<<endl;

int main()
    {
        fio;
        ll a,b,c,d;
        cin>>a>>b>>c>>d;
        cout<<max({a*c,b*d,a*d,b*c})<<endl;
        return 0;
    }