// #define INTERACTIVE
// #define FAST_EXECUTION
#include <bits/stdc++.h>
const long long INF = LONG_LONG_MAX / 2;
const long long MOD = 998244353;
#ifdef ONLINE_JUDGE
#define debug(x) do { } while (0)
#define debug2(x, y) do { } while (0)
#define debug3(x, y, z) do { } while (0)
#define debugendl() do { } while (0)
#define debugarray(a) do { } while (0)
#define debugmatrix(m) do { } while (0)
#else
#define debug(x) cerr << #x << " = " << x << endl
#define debug2(x, y) cerr << #x << " = " << x << ", " << #y << " = " << y << endl
#define debug3(x, y, z) cerr << #x << " = " << x << ", " << #y << " = " << y << ", " << #z << " = " << z << endl
#define debugarray(a) cerr << #a << " = "; for (auto v: a) cerr << v << " "; cerr << endl;
#define debugendl() cerr << endl
#define debugmatrix(m) cerr << #m << " = " << endl; for (auto v: m) { for (auto w: v) cerr << w << " "; cerr << endl; }
#endif
#define LL long long
#define L long
#define ULL unsigned long long
#define I int
#define UI unsigned int
#define D double
#define V(T) std::vector<T>
#define W(T) std::vector<std::vector<T>>
#define S(T) std::set<T>
#define P(T, U) std::pair<T, U>
#define M(T, U) std::map<T, U>
#define ALL(a) a.begin(), a.end()
#define REP(n) for (int t = 0; t < n; ++t)
#define FOR(i, n) for (int i = 0; i < n; ++i)
#define FFOR(i, j, n) for (int i = j; i < n; ++i)
#define FOR_S(i, n, k) for (int i = 0; i < n; i += k)
#define RFOR(i, n) for (int i = n-1; i >= 0; --i)
#define RFOR_S(i, n, k) for (int i = n-1; i >= 0; i -= k)
#define MAX(a, b) (((a) > (b)) ? (a) : (b))
#define MIN(a, b) (((a) < (b)) ? (a) : (b))
#define IN(a, b) (a.find(b) != a.end())
#define MAX_IN(A) *(max_element(A.begin(), A.end()))
#define MIN_IN(A) *(min_element(A.begin(), A.end()))
#define MAX_AT(A) (max_element(A.begin(), A.end()) - A.begin())
#define MIN_AT(A) (min_element(A.begin(), A.end()) - A.begin())
#define SUM(A) accumulate(A.begin(), A.end(), 0LL)
#define PRO(A) accumulate(A.begin(), A.end(), 1LL, multiplies<long long>())
#define COUNT(A, x) count(A.begin(), A.end(), x)
#define EXISTS(A, cond) any_of(A.begin(), A.end(), cond)
#define FORALL(A, cond) all_of(A.begin(), A.end(), cond)
#define GCD(a, b) gcd(a, b)
#define LCM(a, b) (a * b / gcd(a, b))
#define SORT(a) sort(ALL(a))
#define DSORT(a) sort(ALL(a), greater<>())
#define ORD(c) (c-'a')
#define test_cases() LL t; cin >> t; while (t--) solve()
#define endl '\n'
#ifndef INTERACTIVE
#define faster_io() ios_base::sync_with_stdio(0);cin.tie(0);cout.tie(0)
#else
#define faster_io() do { } while (0)
#endif
#ifdef FAST_EXECUTION
#pragma GCC optimize("Ofast")
#pragma GCC target("avx2")
#endif
template<typename A, typename B> std::pair<A, B> operator+(const std::pair<A, B> &a, const std::pair<A, B> &b) { return {a.first + b.first, a.second + b.second}; }
template<typename A, typename B> std::pair<A, B> operator-(const std::pair<A, B> &a, const std::pair<A, B> &b) { return {a.first - b.first, a.second - b.second}; }
template<typename T> std::pair<T, T> operator*(const std::pair<T, T> &a, const T& b) { return {b * a.first, b * a.second}; }
template<typename T> std::pair<T, T> operator*(const T& b, const std::pair<T, T> &a) { return {b * a.first, b * a.second}; }
bool pair_cmp_second(const std::pair<long long, long long> &a, const std::pair<long long, long long> &b) { return a.second < b.second || (a.second == b.second && a.first < b.first); }
template<typename A, typename B> std::ostream& operator<<(std::ostream &out, const std::pair<A, B> &p);
template<typename A, typename B> std::istream& operator>>(std::istream &in, std::pair<A, B> &p);
template<typename T> std::ostream& operator<<(std::ostream &out, const std::vector<T> &v);
template<typename T> std::istream& operator>>(std::istream &in, std::vector<T> &v);
template<typename A, typename B> std::ostream& operator<<(std::ostream &out, const std::pair<A, B> &p) { return out << "(" << p.first << ", " << p.second << ")"; }
template<typename A, typename B> std::istream& operator>>(std::istream &in, std::pair<A, B> &p) { return in >> p.first >> p.second; }
template<typename T> std::ostream& operator<<(std::ostream &out, const std::vector<T> &v) { for (const T &x : v) out << x << " "; return out; }
template<typename T> std::istream& operator>>(std::istream &in, std::vector<T> &v) { for (T &x : v) in >> x; return in; }
LL gcd(LL a, LL b) {
while (b) {
LL t = b;
b = a % b;
a = t;
}
return a;
}
using namespace std;
inline void solve() {
LL n, len; cin >> n >> len;
V(P(LL, LL)) a(n); cin >> a;
double l = 0., r = 1.5e9, mid, curr;
while (r - l > 1e-6) {
mid = (l + r) / 2, curr = 0.;
FOR(i, n) {
double delta = sqrt(mid * mid - a[i].second * a[i].second);
double start = a[i].first - delta, end = a[i].first + delta;
if (start <= curr) curr = MAX(curr, end);
}
if (curr >= len) r = mid;
else l = mid;
}
cout << fixed << setprecision(6) << l << endl;
}
int main() {
faster_io();
// test_cases();
solve();
return 0;
}
