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)

int main()
{
  long long a, b, c, d;
  scanf("%lld %lld %lld %lld", &a, &b, &c, &d);
  long long e[7];
  e[0] = a * c;
  e[1] = b * d;
  e[2] = a * d;
  e[3] = b * c;
  long long ans = e[0];
  int i = 1;
  if ((a <= 0 && b >= 0) || (c <= 0 && d >= 0))
  {
    e[4] = 0;
    while (i < 5)
    {
      if (ans < e[i])
        ans = e[i];
      i++;
    }
  }
  else
  {
    while (i < 4)
    {
      if (ans < e[i])
        ans = e[i];
      i++;
    }
  }
  printf("%lld", ans);
}