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 fastio ios::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL)
#define display(v) for (auto x : v) cout << x << ", "
#define print(x) cout << (#x) << " = [ ";display(x); cout << "]\n"
#define endl '\n'
#define all(x) (x).begin(), (x).end()
#define ceel(x, y) ((x) / (y) + !((x) % (y) == 0))
#define ss second
#define ff first
#define pb push_back
typedef long long int ll;
typedef unsigned long long int ull;
using namespace std;

void __print(int x) {cout << x;}
void __print(long long x) {cout << x;}
void __print(double x) {cout << x;}
void __print(long double x) {cout << x;}
void __print(char x) {cout << '\'' << x << '\'';}
void __print(const string &x) {cout << '\"' << x << '\"';}
void __print(bool x) {cout << (x ? "true" : "false");}
 
template<typename T, typename V>
void __print(const pair<T, V> &x) {cout << '{'; __print(x.first); cout << ','; __print(x.second); cout << '}';}
template<typename T>
void __print(const T &x) {int f = 0; cout << '{'; for (auto &i: x) cout << (f++ ? "," : ""), __print(i); cout << "}";}
void _print() {cout << "]\n";}
template <typename T, typename... V>
void _print(T t, V... v) {__print(t); if (sizeof...(v)) cout << ", "; _print(v...);}
#ifdef INCLUDEWHENOFFLINE
#define debug(x...) cout << "[" << #x << "] = ["; _print(x)
#else
#define debug(x...)
#endif



int main()
{
    fastio;

    ll a, b, c, d;
    cin >> a >> b >> c >> d;
    ll ans = max({a * c, b * d, a * d, b * c});
    cout << ans;

    return 0;
}