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 MOD 1000000007
#define md 998244353
#define INF LLONG_MAX
#define F first
#define S second
#define sz(x) (long long)x.size()
#define vi vector<int>
#define vll vector<long long>
#define vpl vector<pair<long long,long long> >
#define vpi vector<pair<int,int> >
#define pb push_back
#define debug(x) cerr<<#x<<"= "<<x<<endl
#define all(v) v.begin(),v.end()
#define TT ll test;cin>>test; while(test--)
#define rep(i,a,n) for(ll i=a;i<(long long)n;++i)
#define repr(i,n,a) for(ll i=n;i>(long long)a;--i)
#define endl '\n'
#define MAXN 200005
typedef long long ll;
typedef long double ld;
using namespace std;

int main(){
    ios_base::sync_with_stdio(false);cin.tie(NULL);
    ll a,b,c,d;
    cin>> a>> b >> c >>d;
    ll res = -INF;
    res=max({a*c,a*d,b*c,b*d});
    cout<<res;

    

    return 0;
}