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;
#define ll long long int

int main()
{
  ll a,b,c,d;
  cin>>a>>b>>c>>d;
  ll a_p,a_n,b_p,b_n;
  if(a<0 && b<0)
  {
   a_n=a;
    a_p=b;
  }
  else if(a<0 && b>=0)
  {
    a_p=b;
    a_n=a;
  }
  else if(a>=0 && b>0)
  {
   a_p=b;
    a_n=a;
  }
  
  if(c<0 && d<0)
  {
	b_n=c;
    b_p=d;
  }
  else if(c<0 && d>=0)
  {
    b_p=d;
    b_n=c;
  }
  else if(c>=0 && d>0)
  {
   b_p=d;
    b_n=c;
  }
  if((a_p*b_p)>=(a_n * b_n))
  {
   cout<<(a_p*b_p)<<endl; 
  }
  else
  {
   cout<<(a_n*b_n)<<endl; 
  }
  
}