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 Pascal (FPC 3.0.4) (judge verdict: Wrong Answer)

uses
sysutils, math;
 
 
var
a,b,c,d,x,t1,t2: integer;
 
begin
 
read (a);
read (b);
read(c);
read(d);
 
IF (b = 0) AND (c = 0) THEN
begin
	x:= a * c;
    writeln(x);
    exit;
end;
 
IF (a > 0) AND (c > 0) THEN
begin
	x:= b * d;
    writeln(x);
end;
 
IF (b < 0) AND (d < 0) THEN
begin
	x:= a * c;
    writeln(x);
    exit;
end;
 
IF (a < 0) AND (c < 0) THEN
begin
	x:= b * d;
    writeln(x);
    exit;
end;
 
IF (b < 0) AND (d > 0) THEN
begin
	x:= max(a,b) * min(c,d);
    writeln(x);
    exit;
end;

IF (b > 0) AND (d < 0) THEN
begin
	x:= min(a,b) * max(c,d);
    writeln(x);
    exit;
end;
 
end.