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)


// Problem : B - Product Max
// Contest : AtCoder - AtCoder Beginner Contest 178
// URL : https://atcoder.jp/contests/abc178/tasks/abc178_b
// Memory Limit : 1024 MB
// Time Limit : 2000 ms
// Powered by CP Editor (https://github.com/cpeditor/cpeditor)

/*ヽ｀、ヽ｀｀、ヽ｀ヽ｀、、ヽ ｀ヽ 、ヽ｀🌙｀ヽヽ｀ヽ、ヽ｀
ヽ｀、ヽ｀｀、ヽ 、｀｀、 ｀、ヽ｀ 、｀ ヽ｀ヽ、ヽ ｀、ヽ｀｀、
ヽ、｀｀、｀、ヽ｀｀、 、ヽヽ｀、｀、、ヽヽ、｀｀、 、 ヽ｀、
ヽ｀｀、 ヽ｀ヽ｀、、ヽ ｀ヽ 、 🚶ヽ｀｀｀｀ヽヽヽ｀、、ヽ｀、、ヽ*/
#include <bits/stdc++.h> 
#pragma GCC optimize ("O3")
#pragma GCC target ("sse4")
 
#include <bits/stdc++.h>
#include <ext/pb_ds/tree_policy.hpp>
#include <ext/pb_ds/assoc_container.hpp>
 
 
using namespace std;
using namespace __gnu_pbds;
 
typedef long long   ll;
typedef long double ld;
typedef complex< ld > cd;
 
typedef pair<int, int> pi;
typedef pair<ll, ll>   pl;
typedef pair<ld, ld>   pd;
 
typedef vector< int > vi;
typedef vector< ld >  vd;
typedef vector< ll >  vl;
typedef vector< pi >  vpi;
typedef vector< pl >  vpl;
typedef vector< cd >  vcd;
 
#define l00p(i, a, b) for (int i=a; i<(b); i++)
#define loop(i, a)    for (int i=0; i<(a); i++)
#define rep1(i, a, b) for (int i = (b)-1; i >= a; i--)
#define rep(i, a)     for (int i = (a)-1; i >= 0; i--)
#define trav(a, x)    for (auto& a : x)
#define uid(a, b)     uniform_int_distribution<int>(a, b)(rng)
#define vt vector
#define bug(x) cout<<#x<<"="<<x<<endl;

#define sz(x) (int)(x).size()
#define mp make_pair
#define pb push_back
#define f  first
#define s  second
#define lb lower_bound
#define ub upper_bound
#define all(x) x.begin(), x.end()
#define rall(x) x.rbegin(), x.rend()
#define ins insert
//#define MOD 998244353
 
template<class T> bool ckmin(T& a, const T& b) { return b < a ? a = b, 1 : 0; }
template<class T> bool ckmax(T& a, const T& b) { return a < b ? a = b, 1 : 0; }

mt19937 rng(chrono::steady_clock::now().time_since_epoch().count());

const ld pii=3.14159265359; 
const int MOD = 1000000007;
const char cl = '\n';
const ll INF = 1e18;
const int MX = 100001; //check the limits, dummy

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0); 
	ll a,b,c,d;
	cin>>a>>b>>c>>d;
	ll ans=a*c;
	ckmax(ans,a*d);
	ckmax(ans,b*c);
	ckmax(ans,b*d);
	cout<<ans;
	return 0;
}
// read the question correctly (ll vs int)
// template by bqi343