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)

//
//  main.c
//  atcoder
//
//  Created by k20043kk on 2020/09/13.
//  Copyright © 2020 AIT. All rights reserved.
//

#include <stdio.h>

int main(int argc, const char * argv[]) {
    long long int a,b,c,d;
    scanf("%lld %lld %lld %lld",&a,&b,&c,&d);
    long long int box[4];
    box[0]=a*c;
    box[1]=a*d;
    box[2]=b*c;
    box[3]=b*d;
    long long int max=-999999999999999999;
    for(int i=0;i<4;i++){
        //printf("%lld\n",box[i]);
        if(max<box[i]){
            
            max=box[i];
        }
    }
    printf("%lld\n",max);
    return 0;
}