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 <stdio.h>
typedef long long ll;
int main(){
    ll a,b,c,d;
    ll ans[5];
    scanf("%lld%lld%lld%lld",&a,&b,&c,&d);
    ans[0] = a*c;
    ans[1] = a*d;
    ans[2] = b*c;
    ans[3] = b*d;
    int i,j;
    ll swap;
    for(i=0;i<4;i++){
        for(j=i+1;j<4;j++){
            if(ans[i] > ans[j]){
                swap = ans[i];
                ans[i] = ans[j];
                ans[j] = swap;
            }
        }
    }
    printf("%lld\n",ans[3]);
    return 0;
}