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;
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
const long double pi=acos(-1);
#define x  first
#define y  second
#define read(n,a) for(int i=0;i<n;i++)cin>>a[i];
#define rep(i,z,n)for(int i=z;i<n;i++)

ll a[200002]={};
//int b[1000002]={};
ll n,m;

int main()
{
    int t=1;
    //cin>>t;
    while(t--)
    {
        ll a,b,c,d;
        cin>>a>>b>>c>>d;
       ll ans=max(max(a,b)*max(c,d),min(a,b)*max(c,d));
       ans=max(ans,min(a,b)*min(c,d));
       ans=max(ans,max(a,b)*min(c,d));
       cout<<ans;
    }
    return 0;
}