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 Ruby (2.7.1) (judge verdict: Wrong Answer)

a,b,c,d = gets.chomp.split(" ").map(&:to_i)

if (a >= 0) && (c >= 0)
  puts (b*d)
elsif (b <= 0) && (d <= 0)
  puts (a*c)
elsif (b <= 0) && (c >= 0)
  puts (b*c)
elsif (d <= 0) && (a >= 0)
  puts (a*d)
elsif (b<=0) && (c<=0) && (d >=0 )
  puts (a*c)
elsif (d<= 0) && (a<=0) && (b>=0)
  puts (a*c)
elsif (c>=0) && (b>=0) && (a<= 0)
  puts (b*d)
elsif (a>=0) && (d>=0) && (c<=0)
  puts (b*d)
end