Armistice Area Apportionment
After a drawn-out mooclear arms race, Farmer John and the Mischievous Mess Makers have finally agreed to establish peace. They plan to divide the territory of Bovinia with a line passing through at least two of the *n* outposts scattered throughout the land. These outposts, remnants of the conflict, are located at the points (*x*1,<=*y*1),<=(*x*2,<=*y*2),<=...,<=(*x**n*,<=*y**n*).

In order to find the optimal dividing line, Farmer John and Elsie have plotted a map of Bovinia on the coordinate plane. Farmer John's farm and the Mischievous Mess Makers' base are located at the points *P*<==<=(*a*,<=0) and *Q*<==<=(<=-<=*a*,<=0), respectively. Because they seek a lasting peace, Farmer John and Elsie would like to minimize the maximum difference between the distances from any point on the line to *P* and *Q*.

Formally, define the difference of a line  relative to two points *P* and *Q* as the smallest real number *d* so that for all points *X* on line , |*PX*<=-<=*QX*|<=≤<=*d*. (It is guaranteed that *d* exists and is unique.) They wish to find the line  passing through two distinct outposts (*x**i*,<=*y**i*) and (*x**j*,<=*y**j*) such that the difference of  relative to *P* and *Q* is minimized.
The first line of the input contains two integers *n* and *a* (2<=≤<=*n*<=≤<=100<=000, 1<=≤<=*a*<=≤<=10<=000) — the number of outposts and the coordinates of the farm and the base, respectively.

The following *n* lines describe the locations of the outposts as pairs of integers (*x**i*,<=*y**i*) (|*x**i*|,<=|*y**i*|<=≤<=10<=000). These points are distinct from each other as well as from *P* and *Q*.
Print a single real number—the difference of the optimal dividing line. Your answer will be considered correct if its absolute or relative error does not exceed 10<=-<=6. 

Namely: let's assume that your answer is *a*, and the answer of the jury is *b*. The checker program will consider your answer correct, if .
In the first sample case, the only possible line <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/c7c068229f25f741e2c902b657ba04a42feb0752.png" style="max-width: 100.0%;max-height: 100.0%;"/> is *y* = *x* - 1. It can be shown that the point *X* which maximizes |*PX* - *QX*| is (13, 12), with <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/d4f8c9a4f500c322cb3725c981acd02ebf8d8b35.png" style="max-width: 100.0%;max-height: 100.0%;"/>, which is <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/f488f414e882e7593bfa43cb26e56aaa8072b748.png" style="max-width: 100.0%;max-height: 100.0%;"/>.

In the second sample case, if we pick the points (0, 1) and (0,  - 3), we get <img align="middle" class="tex-formula" src="https://espresso.codeforces.com/c7c068229f25f741e2c902b657ba04a42feb0752.png" style="max-width: 100.0%;max-height: 100.0%;"/> as *x* = 0. Because *PX* = *QX* on this line, the minimum possible difference is 0.