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: Accepted)

var a,b,c,d,ll,lr,rl,rr,tmp:int64;
begin
readln(a,b,c,d);
ll:=a*c;
rl:=b*c;
lr:=a*d;
rr:=b*d;
tmp:=-1000000000 * 1000000000;
if(ll>=tmp)then tmp:=ll;
if(rl>=tmp)then tmp:=rl;
if(lr>=tmp)then tmp:=lr;
if(rr>=tmp)then tmp:=rr;
writeln(tmp);
end.