#include <iostream>
#include <string>
#include <vector>
#include <algorithm>
#include <iomanip>
#include <set>
#include <map>
#include <numeric>
#include <iomanip>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <queue>
#include <deque>
#include <stack>
#include <cmath>
#include <tuple>
#include <cassert>
#include <array>
#include <list>
#include <random>
#include <initializer_list>
using namespace std;
using i64 = long long;
using u64 = unsigned long long;
using db = double;
using ld = long double;
constexpr i64 INF = 1E18;
constexpr i64 MIN = -INF;
constexpr i64 MAX = INF;
constexpr int N = 1E4 + 10;
struct Point {
db x, y;
};
db dist(Point& a, Point& b) {
db dx = abs(a.x - b.x), dy = abs(a.y - b.y);
return sqrt(dx * dx + dy * dy);
}
db calc(Point& a, Point& b) {
return (b.x * b.x + b.y * b.y - a.x * a.x - a.y * a.y) / (2 * (b.x - a.x));
}
void solve() {
int n;
db L;
cin >> n >> L;
vector<Point> points;
for (int i = 0; i < n; ++i) {
db x, y;
cin >> x >> y;
y = abs(y);
while (!points.empty() && (points.back().x == x && points[i].y > y)) {
points.pop_back();
}
if (points.empty() || points.back().x != x) {
points.push_back({ x, y });
}
}
vector<Point> t;
for (int i = 0; i < points.size(); ++i) {
while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) >= calc(t[t.size() - 1], points[i])) {
t.pop_back();
}
t.push_back(points[i]);
}
reverse(t.begin(), t.end());
while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) <= 0) {
t.pop_back();
}
reverse(t.begin(), t.end());
while (t.size() > 1 && calc(t[t.size() - 2], t[t.size() - 1]) >= L) {
t.pop_back();
}
points = t;
Point A = { 0, 0 };
Point B = { L, 0 };
db ans = max(dist(A, points[0]), dist(B, points.back()));
for (int i = 1; i < points.size(); ++i) {
Point tmp = { calc(points[i - 1], points[i]), 0 };
ans = max(ans, dist(points[i], tmp));
}
cout << ans << '\n';
}
int main() {
ios_base::sync_with_stdio(0);
cin.tie(0);
cout << fixed << setprecision(10);
int t = 1;
/*cin >> t;*/
while (t--) {
solve();
}
return 0;
}
