You know, it's hard to conduct a show with lots of participants and spectators at the same place nowadays. Still, you are not giving up on your dream to make a car crash showcase! You decided to replace the real cars with remote controlled ones, call the event "Remote Control Kaboom Show" and stream everything online.
For the preparation you arranged an arena — an infinite 2D-field. You also bought

remote controlled cars and set them up on the arena. Unfortunately, the cars you bought can only go forward without turning left, right or around. So you additionally put the cars in the direction you want them to go.
To be formal, for each car

(

) you chose its initial position (

) and a direction vector (

). Moreover, each car has a constant speed

units per second. So after car

is launched, it stars moving from (

) in the direction (

) with constant speed

.
The goal of the show is to create a car collision as fast as possible! You noted that launching every car at the beginning of the show often fails to produce any collisions at all. Thus, you plan to launch the

-th car at some moment

. You haven't chosen

, that's yet to be decided. Note that it's not necessary for

to be integer and

is allowed to be equal to

for any

.
The show starts at time

. The show ends when two cars

and

(

) collide (i. e. come to the same coordinate at the same time). The duration of the show is the time between the start and the end.
What's the fastest crash you can arrange by choosing all

? If it's possible to arrange a crash then print the shortest possible duration of the show. Otherwise, report that it's impossible.