#include "bits/stdc++.h"
#include <type_traits>
using namespace std;
#pragma GCC optimize("Ofast")
#pragma GCC target("avx,avx2,fma")
#pragma GCC optimization("unroll-loops")
// ============ Macros starts here ============
int recur_depth = 0;
#ifdef DEBUG
#define dbg(x) {++recur_depth; auto x_=x; --recur_depth; cerr<<string(recur_depth, '\t')<<"\e[91m"<<__func__<<":"<<__LINE__<<"\t"<<#x<<" = "<<x_<<"\e[39m"<<endl;}
#else
#define dbg(x)
#endif // DEBUG
template<typename Ostream, typename Cont>
typename enable_if<is_same<Ostream, ostream>::value, Ostream&>::type operator<<(Ostream& os, const Cont& v) {
os << "{";
for (auto& x : v) { os << x << ", "; }
return os << "}";
}
template<typename Ostream, typename ...Ts>
Ostream& operator<<(Ostream& os, const pair<Ts...>& p) {
return os << "{" << p.first << ", " << p.second << "}";
}
#define readFast \
ios_base::sync_with_stdio(false); \
cin.tie(0); \
cout.tie(0);
#ifdef LOCAL
#define read() ifstream fin("date.in.txt")
#else
#define read() readFast
#endif // LOCAL
// ============ Macros ends here ============
#define fin cin
#define ll long long
#define sz(x) (int)(x).size()
#define all(v) v.begin(), v.end()
#define output(x) (((int)(x) && cout << "YES\n") || cout << "NO\n")
#define LSB(x) (x & (-x))
#define test cout << "WORKS\n";
vector<pair<double, double>> a;
int n;
double L;
double dist(int i, long double d) {
// dbg(sqrt(d * d - a[i].second * a[i].second));
return sqrt(d * d - a[i].second * a[i].second);
}
bool check(double d) {
double maxRight = 0;
for (int i = 0; i < n; ++i) {
// if (a[i].second > d) {
// continue;
// }
auto c1 = dist(i, d);
// cout << c1 * c1 << " " << a[i].second * a[i].second << " " << d * d << '\n';
// cout << a[i].first - c1 << " " << a[i].first + c1 << '\n';
auto left = a[i].first - c1;
// cout << maxRight - left << " " << -(1e-3) << '\n';
if (maxRight >= left) {
maxRight = max(maxRight, a[i].first + c1);
}
}
// cout << maxRight - L << '\n';
return maxRight >= L;
}
int main() {
read();
fin >> n >> L;
a.resize(n);
for (int i = 0; i < n; ++i) {
fin >> a[i].first >> a[i].second;
}
// dbg(check(1.11777));
double l = 1, r = 1.5e9, mid;
while (r - l > 1e-3) {
mid = (l + r) / 2;
if (check(mid)) {
r = mid;
} else {
l = mid;
}
}
cout << fixed << setprecision(4) << r << '\n';
return 0;
} /*stuff you should look for !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
* test the solution with the given example
* int overflow, array bounds, matrix bounds
* special cases (n=1?)
* do smth instead of nothing and stay organized
* WRITE STUFF DOWN
* DON'T GET STUCK ON ONE APPROACH
~Benq~*/
