#include <bits/stdc++.h>
using namespace std;
struct Point {
double x, y;
Point() : x(0), y(0) {}
Point(double x, double y) : x(x), y(y) {}
};
// Function to calculate the critical point
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));
}
// Function to calculate the distance between two points
double dist(Point a, Point b) {
return sqrt((a.x - b.x) * (a.x - b.x) + (a.y - b.y) * (a.y - b.y));
}
int main() {
ios::sync_with_stdio(false);
cin.tie(0);
int N, L;
cin >> N >> L;
vector<Point> needed; // Used instead of LinkedList in Java
for (int i = 0; i < N; i++) {
Point cur;
cin >> cur.x >> cur.y;
if (cur.y < 0) cur.y = -cur.y; // Treat negative y the same as positive y
// Remove points with the same x-coordinate but further away y-coordinates
if (!needed.empty() && needed.back().x == cur.x) {
if (cur.y >= needed.back().y) {
continue;
} else {
needed.pop_back();
}
}
// Find the crosses and remove points that don't form a convex shape
while (needed.size() > 1 && criticalPoint(needed[needed.size() - 2], needed.back()) > criticalPoint(needed.back(), cur)) {
needed.pop_back();
}
needed.push_back(cur);
}
// Remove points from the front that have critical points less than 0
while (needed.size() > 1 && criticalPoint(needed[0], needed[1]) < 0) {
needed.erase(needed.begin());
}
// Remove points from the back that exceed the length L
while (needed.size() > 1 && criticalPoint(needed[needed.size() - 2], needed.back()) > L) {
needed.pop_back();
}
double ans = 0;
// Loop over the points and calculate the maximum distance
for (int x = 0; x < needed.size(); x++) {
Point left(0, 0);
Point right(L, 0);
if (x > 0) left.x = criticalPoint(needed[x], needed[x - 1]);
if (x < needed.size() - 1) {
right.x = criticalPoint(needed[x], needed[x + 1]);
}
// If points are out of bounds, skip
if (left.x < 0 || right.x > L || right.x < 0 || left.x > L) continue;
// Update the answer with the maximum distance
ans = max(ans, max(dist(needed[x], left), dist(needed[x], right)));
}
cout << fixed << ans << "\n";
return 0;
}
