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(){
  int a , b , c , d;
  scanf("%d %d %d %d", &a , &b , &c ,&d);
  long long ac , ad , bc , bd;
  ac = (long long)a * (long long)c;
  ad = (long long)a * (long long)d;
  bc = (long long)b * (long long)c;
  bd = (long long)b * (long long)d;
  long long max = ac;
  if(max < ad)
    max = ad;
  if(max < bc)
    max = bc;
  if(max < bd)
    max = bd;
  printf("%lld\n",max);
  return 0;
}