#include <bits/stdc++.h>
using namespace std;
namespace shortages {
using ll = long long;
using ull = unsigned long long;
using uint = unsigned int;
using ld = long double;
template <typename T>
using vec = vector<T>;
template <typename T>
using vv = vector<vector<T>>;
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const pair<T1, T2>& pa) {
os << pa.first << ' ' << pa.second;
return os;
}
template <typename T1, typename T2>
istream& operator>>(istream& is, pair<T1, T2>& pa) {
is >> pa.first >> pa.second;
return is;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<T>& vec) {
for (size_t i = 0; i < vec.size(); ++i) {
os << vec[i];
if (i + 1 < vec.size())
os << ' ';
}
os << '\n';
return os;
}
template <typename T1, typename T2>
ostream& operator<<(ostream& os, const vector<pair<T1, T2>>& vec) {
for (size_t i = 0; i < vec.size(); ++i) {
os << vec[i].first << ' ' << vec[i].second;
if (i + 1 < vec.size())
os << '\n';
}
return os;
}
template <typename T>
ostream& operator<<(ostream& os, const vector<vector<T>>& vec) {
for (size_t i = 0; i < vec.size(); ++i)
os << vec[i];
os << '\n';
return os;
}
template <typename T>
istream& operator>>(istream& is, vector<T>& vec) {
for (auto& x : vec)
is >> x;
return is;
}
#define pint pair<int,int>
#define pll pair<ll, ll>
#define vi vec<int>
#define vll vec<ll>
#define vvi vec<vec<int>>
#define vvll vec<vec<ll>>
#define all(v) v.begin(), v.end()
}
using namespace shortages;
bool ith_bit(int n, int i) {
return (n >> i) & 1;
}
void answer(bool ans) {
if (ans)
cout << "Yes\n";
else
cout << "No\n";
}
constexpr ll INF = 1e18;
constexpr ll M = 998244353;
ld d(pint p, pint q) {
ll x=p.first,y=p.second,z=q.first,t=q.second;
return (ld) (z * z + t * t - x * x - y*y) / (2 * (z - x));
}
ld dist(pint p, pair<ld, ld> q) {
ld x=p.first,y=p.second,z=q.first,t=q.second;
return sqrt((x - z) * (x - z) + (y - t) * (y - t));
}
void solve() {
int n, l;
cin >> n >> l;
vec<pint> a;
for (int i = 0; i < n; ++i) {
pint p;
cin >> p;
if (!a.empty()) {
pint q = a.back();
if (q.first == p.first) {
a.pop_back();
pint r = {q.first, min(abs(p.second), abs(q.second))};
a.push_back(r);
}
else
a.push_back(p);
}
else
a.push_back(p);
}
stack<pint> s;
for (auto p : a) {
while (s.size() >= 2) {
pint q = s.top(); s.pop();
if (d(p, q) >= d(q, s.top())) {
s.push(q);
break;
}
}
s.push(p);
}
vec<pint> v;
while (!s.empty()) {
pint q = s.top(); s.pop();
v.push_back(q);
}
reverse(all(v));
ld res = 0;
for (int i = 0; i < v.size() - 1; ++i) {
ld val = d(v[i], v[i + 1]);
if (val >= 0 && val <= l)
res = max(res, dist(v[i], {val, 0}));
}
res = max(res, dist(v.front(), {0, 0}));
res = max(res, dist(v.back(), {l, 0}));
cout << fixed << setprecision(6) << res << '\n';
}
int main() {
ios_base::sync_with_stdio(false);
//cin.tie(NULL);
//freopen("paintbarn.in", "r", stdin);
//freopen("paintbarn.out", "w", stdout);
int test = 1;
//cin >> test;
while (test--)
solve();
return 0;
}
