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 <algorithm>
#include<iostream>
#include<vector>
#include<deque>
#include<queue>
#include<stack>
#include<list>
#include<map>
#include<set>
#include<string>
#include <sstream>
#include<bitset>

#include<stdlib.h>
#include<string.h>
#include<math.h>
#include<limits.h>
const int INF = 0x7fffffff;
using lll = long long;
using ull = unsigned long long;
using namespace std;


int main(){
  lll ii,jj,kk;
  vector<int> ret;
  lll a,b,c,d;

  cin >> a >> b >> c >> d;
  
  lll max;
  if(a >= 0 && c >= 0){
    max = b * d;
  }
  else if(b < 0 && c>= 0){
    max = b * c;
  }
  else if(a>= 0 && d < 0){
    max = a * d;
  }
  else{
    max = a * c;
  }
  cout << max << endl;
  return 0;
}