#include <iostream>
#include <vector>
#include <cmath>
#include <iomanip>
#include <algorithm>
using namespace std;
typedef long double ld;
struct Tower {
ld x, y;
};
// Intersection of (x-x1)^2 + y1^2 = (x-x2)^2 + y2^2
ld intersect(Tower a, Tower b) {
return (b.x * b.x + b.y * b.y - a.x * a.x - a.y * a.y) / (2.0 * (b.x - a.x));
}
ld get_dist(Tower t, ld x) {
return sqrtl((t.x - x) * (t.x - x) + t.y * t.y);
}
int main() {
ios::sync_with_stdio(0); cin.tie(0);
int n; ld l;
if (!(cin >> n >> l)) return 0;
vector<Tower> input(n);
for(int i=0; i<n; ++i) cin >> input[i].x >> input[i].y;
// 1. Pre-process: Filter duplicate X, keep smallest |y|
vector<Tower> filtered;
for(auto &t : input) {
if(!filtered.empty() && filtered.back().x == t.x) {
if(abs(t.y) < abs(filtered.back().y)) filtered.back() = t;
} else filtered.push_back(t);
}
// 2. Build the Stack (Lower Envelope)
// We use a vector as a stack so we can iterate through it at the end
vector<Tower> st;
for(auto &t : filtered) {
while(st.size() >= 2) {
if(intersect(st[st.size()-2], st.back()) >= intersect(st.back(), t))
st.pop_back();
else break;
}
st.push_back(t);
}
// 3. Find Max Distance by checking critical points
ld max_d = 0;
// Check x = 0: Which tower in the stack is closest to 0?
// Because intersections are increasing, we find the first tower
// whose intersection with the next is > 0.
int first_idx = 0;
while(first_idx + 1 < st.size() && intersect(st[first_idx], st[first_idx+1]) <= 0) {
first_idx++;
}
max_d = max(max_d, get_dist(st[first_idx], 0));
// Check x = L: Which tower in the stack is closest to L?
int last_idx = st.size() - 1;
while(last_idx - 1 >= 0 && intersect(st[last_idx-1], st[last_idx]) >= l) {
last_idx--;
}
max_d = max(max_d, get_dist(st[last_idx], l));
// Check all intersections between first_idx and last_idx
for(int i = first_idx; i < last_idx; ++i) {
ld x_int = intersect(st[i], st[i+1]);
// Only consider intersections within the highway bounds
if(x_int > 0 && x_int < l) {
max_d = max(max_d, get_dist(st[i], x_int));
}
}
cout << fixed << setprecision(6) << (double)max_d << endl;
return 0;
}
