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;
int main(){
    cin.tie(0);
    ios_base::sync_with_stdio(false);
    long long int a,b,c,d;
    cin >> a >> b >> c >> d;
    if(a>=0){
        if(d>=0) cout << d*b;
        else{
            cout << a*d;
        }
    }
    else if(b>=0){
        long long int ans = a*c > b*d ? a*c : b*d;
        cout << ans;
    }
    else{ // b < 0
        if(c>=0) cout << c*b;
        else{
            cout << a*c;
        }
    }
    return 0;
}