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 PyPy3 (7.3.0) (judge verdict: Wrong Answer)

def calc(intA,intB,intC,intD):
    #b>0　d>0　→x × y>0 
    if b>0 and d>0:
       ret = b*d
    elif b<=0 and d<=0:
       ret = a*c
    elif b<=0 and d>0:
       ret = b*c
    elif b>0 and d<=0:
       ret = a*d
    return ret

a,b,c,d = map(int,(input()).split())

print(calc(a,b,c,d))