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>

int main (void){
    long long int a,b,c,d;
    long long int ans;

    scanf("%lld %lld %lld %lld",&a,&b,&c,&d);


    if(a<=0){
        if(c<=0){
            ans=a*c;    //とりま

            if(ans<b*d){
                ans=b*d;

            }

        }else if(b<0){
            ans=b*c;

        }else{
            ans=b*d;
        }

    }else{ //0<a
        if(d<=0){
            ans=a*d;
        }else{
            ans=b*d;
        }
    }

    printf("%lld",ans);

    return 0 ;
}