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>
#include <unordered_map>
using namespace std;

#define lson rt << 1
#define rson rt << 1 | 1
#define mid ((l + r) >> 1)
#define Lson l, mid, lson
#define Rson mid + 1, r, rson
const int MAXN = 1e5 + 20;
using pa = pair<int, int>;
using ll = long long;


int dp[MAXN][9][9];
const int MOD = 1e9 + 7;
int main() {
    ll l1, r1, l2, r2;
    cin >> l1 >> r1 >> l2 >> r2;
    cout << max(l1 * l2, max(l1 * r2, max(r1 * l2, r1 * r2))) << endl; 
}