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>

#define int long long
#define counter(m)     for(int i=0;i<m;i++)
#define gcd            __gcd
#define endl           "\n"
#define pb             emplace_back
#define setbits(x)     __builtin_popcountll(x)
#define zrobits(x)     __builtin_ctzll(x)
#define mod            1000000007
#define mod2           998244353
#define maxe           *max_element
#define mine           *min_element
#define inf            1e18
#define deci(x, y)      fixed<<setprecision(y)<<x
#define w(t)           int t; cin>>t; while(t--)
#define nitin          ios_base::sync_with_stdio(false); cin.tie(NULL)
#define PI             3.141592653589793238
using namespace std;

int32_t main() {
    nitin;
    int a,b,c,d;
    cin>>a>>b>>c>>d;
    cout<<max(a*c,max(a*d,max(b*c,b*d)))<<endl;
    return 0;
}