Colin recently watched the movie
Dune: Part Two and was deeply impressed by the scene in which Paul Atreides summons and rides a giant sandworm!
Colin noticed that the timing of summoning sandworms is very important. There are always so many mysteries hidden under the calm dunes! Therefore, he modeled "Summoning Sandworms" and designed a problem for you:
To simplify the problem, we describe the topography of the dunes with a one-dimensional numerical axis. There are

sandworms moving parallel to the number axis. Specifically, at the initial time

, the body of the

-th sandworm can be described by the segment
![[l_i,r_i]](https://www.nowcoder.com/equation?tex=%5Bl_i%2Cr_i%5D)
(thus, the length of the

-th sandworm is

), and it will move in the positive direction of the number axis at a speed of

per second. That is, at time

, the body of the

-th worm can be described by the segment
![[l_i+v_i\times t,r_i+v_i\times t]](https://www.nowcoder.com/equation?tex=%5Bl_i%2Bv_i%5Ctimes%20t%2Cr_i%2Bv_i%5Ctimes%20t%5D)
.
Your position is at coordinate

and you can choose
any nonnegative real number time

to summon sandworms passing through your position (i.e. at time

, the coordinate
![x\in [l_i+v_i\times t',r_i+v_i\times t']](https://www.nowcoder.com/equation?tex=x%5Cin%20%5Bl_i%2Bv_i%5Ctimes%20t'%2Cr_i%2Bv_i%5Ctimes%20t'%5D)
). However, there may be more than one sandworm passing through your position at this moment. In this case, you can only summon
the shortest one among these sandworms.
There's nothing more exciting than summoning a giant sandworm! So Colin wants to know, what is the longest length of sandworm you can possibly summon.