#pragma GCC optimize("Ofast,unroll-loops,no-stack-protector")
// #pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,avx2,tune=native")
#include <bits/stdc++.h>
using namespace std;
// #include <ext/pb_ds/assoc_container.hpp>
// #include <ext/pb_ds/tree_policy.hpp>
// using namespace __gnu_pbds;
// template<typename T> using oset = tree<T, null_type, less<T>, rb_tree_tag, tree_order_statistics_node_update>;
#define ll long long
#define ull unsigned long long
#define ld long double
#define pii pair<int, int>
#define pll pair<ll, ll>
#define pli pair<ll, int>
#define plpll pair<ll, pll>
#define pipii pair<int, pii>
#define plpii pair<ll, pii>
#define pipll pair<int, pll>
#define lll tuple<ll, ll, ll>
#define iii tuple<int, int, int>
#define lii tuple<ll, int, int>
#define lli tuple<ll, ll, int>
#define md 1000000007LL
#define linf 0x3f3f3f3f3f3f3f3f
#define inf 0x3f3f3f3f
#define lninf (ll)0xc0c0c0c0c0c0c0c0
#define ninf (int)0xc0c0c0c0
#define bruh ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
#define ss << ' ' <<
#ifdef wizard
#define usaco(x)
#else
#define usaco(x) ifstream cin(#x ".in"); ofstream cout(#x ".out");
#endif
template<class T1, class T2>
istream& operator>>(istream& in, pair<T1, T2>& p) {
return in >> p.first >> p.second;
}
template<class T1, class T2>
ostream& operator<<(ostream& out, const pair<T1, T2>& p) {
return out << p.first << ' ' << p.second;
}
template<size_t I = 0, typename... Ts>
typename enable_if<I == sizeof...(Ts), istream&>::type
read_tuple(istream& in, tuple<Ts...>& t) { return in; }
template<size_t I = 0, typename... Ts>
typename enable_if<I < sizeof...(Ts), istream&>::type
read_tuple(istream& in, tuple<Ts...>& t) {
in >> get<I>(t);
return read_tuple<I + 1>(in, t);
}
template<typename... Ts>
istream& operator>>(istream& in, tuple<Ts...>& t) {
return read_tuple(in, t);
}
template<size_t I = 0, typename... Ts>
typename enable_if<I == sizeof...(Ts), void>::type
write_tuple(ostream& out, const tuple<Ts...>&) {}
template<size_t I = 0, typename... Ts>
typename enable_if<I < sizeof...(Ts), void>::type
write_tuple(ostream& out, const tuple<Ts...>& t) {
if (I) out << ' ';
out << get<I>(t);
write_tuple<I + 1>(out, t);
}
template<typename... Ts>
ostream& operator<<(ostream& out, const tuple<Ts...>& t) {
write_tuple(out, t);
return out;
}
template<typename T>
istream& operator>>(istream& in, vector<T>& v) {
for (auto& x : v) in >> x;
return in;
}
template<typename T>
ostream& operator<<(ostream& out, const vector<T>& v) {
for (size_t i = 0; i < v.size(); ++i)
out << (i ? " " : "") << v[i];
return out;
}
int n;
ld l, x[1000000], y[1000000], L = 0, R = 1.42e9, ans;
int main() {
bruh;
cin >> n >> l;
for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
while (R - L >= 1e-3) {
ld mid = (L+R)/(ld)2;
ld last = 0;
for (int i = 0; i < n; i++) {
if (mid < y[i]) continue;
ld d = sqrt(mid*mid - y[i]*y[i]);
if (x[i] - d <= last) last = max(last, x[i] + d);
}
if (last >= l) R = mid, ans = mid;
else L = mid;
}
cout << fixed << setprecision(4) << ans;
}
