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>
#define MAX(a,b) ((a)>(b) ?(a) : (b))
#define MIN(a,b) ((a)<(b) ?(a) : (b))
#define ABS(a) ((a)>0 ?(a) : (-a))
int main(void){
  long long int a,b,c,d;
  scanf("%lld%lld%lld%lld",&a,&b,&c,&d);
  //printf("%lld-%lld-%lld-%lld\n",b*d,a*c,a*d,b*c);
  printf("%lld\n",MAX(MAX(b*d,a*c),MAX(a*d,b*c)));
  return 0;
}