import java.awt.*;
import java.io.*;
import java.util.*;
public class mobile {
static class Point {
double x, y;
public Point() {
}
public Point(double x, double y) {
this.x = x;
this.y = y;
}
}
static double criticalPoint(Point a, Point b) {
return (a.x*a.x - b.x*b.x + a.y*a.y - b.y*b.y) / (2*(a.x-b.x));
}
static double dist(Point a, Point b) {
return Math.sqrt((a.x-b.x)*(a.x-b.x) + (a.y-b.y)*(a.y-b.y));
}
public static void main(String... args) throws IOException {
// BufferedReader reader = new BufferedReader(new FileReader("input.in"));
BufferedReader reader = new BufferedReader(new InputStreamReader(System.in));
PrintWriter writer = new PrintWriter(new BufferedWriter(new OutputStreamWriter(System.out)));
StringTokenizer st = new StringTokenizer(reader.readLine());
int N = Integer.parseInt(st.nextToken());
int L = Integer.parseInt(st.nextToken());
LinkedList<Point> needed = new LinkedList<>(); // Java Queues don't have indices so we will use ArrayList and 2P
// this should already be sorted
for (int i = 0; i < N; i++) {
Point cur = new Point();
st = new StringTokenizer(reader.readLine());
cur.x = Integer.parseInt(st.nextToken());
cur.y = Integer.parseInt(st.nextToken());
if (cur.y < 0) cur.y = -cur.y; // negative y and positive y are treated the same. you can use the orthocenter to prove this.
if (needed.size() > 0 && needed.peekLast().x == cur.x) { // if x coord is the same remove farther away y-coord points.
if (cur.y >= needed.peekLast().y) {
continue;
} else if (cur.y < needed.peekLast().y) {
needed.removeLast();
}
}
// find crosses
while ( needed.size() > 1 && criticalPoint(needed.get(needed.size() - 2), needed.peekLast()) >
criticalPoint(needed.peekLast(), cur)) {
needed.removeLast();
}
needed.addLast(cur);
}
while (needed.size() > 1 && criticalPoint(needed.get(0), needed.get(1)) < 0) {
needed.removeFirst();
}
while (needed.size() > 1 && criticalPoint(needed.get(needed.size() - 2), needed.peekLast()) > L) {
needed.removeLast();
} // remove out of bounds points. but must keep at least one.
double ans = 0;
for (int x = 0; x < needed.size(); x++) {
Point left = new Point(0, 0);
Point right = new Point(L, 0);
if (x > 0) left.x = criticalPoint(needed.get(x), needed.get(x - 1));
if (x < needed.size() - 1) {
right.x = criticalPoint(needed.get(x), needed.get(x + 1));
}
if (left.x < 0 || right.x > L || right.x < 0 || left.x > L) continue;
ans = Math.max(ans, Math.max(dist(needed.get(x), left), dist(needed.get(x), right)));
}
writer.println(ans);
writer.close();
}
}
