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>
#include <string.h>
#include <ctype.h>
#include<math.h>
int main(){
    long long a,b,c,d, eq1=0, eq2=0, eq3=0, eq4=0;
    scanf("%lld %lld %lld %lld", &a,&b,&c,&d);
    eq1= a*c;
    eq2= a*d;
    eq3= b*c;
    eq4= b*d;
    if(eq1>= eq2 && eq1>= eq3 && eq1>= eq4)
        printf("%lld", eq1);
    else if(eq2>= eq1 && eq2>= eq3 && eq2>= eq4)
        printf("%lld", eq2);
    else if(eq3>= eq1 && eq3>= eq2 && eq3>= eq4)
        printf("%lld", eq3);
    else if(eq4>= eq1 && eq4>= eq3 && eq4>= eq2)
        printf("%lld", eq4);
    printf("\n");
    return 0;
}