#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace std;
using namespace __gnu_pbds;
#pragma GCC target ("avx2")
#pragma GCC optimize ("O3")
#pragma GCC optimize ("unroll-loops")
#pragma GCC optimize("fast-math")
#define ll int
#define ld double
#define vi vector<ll>
#define endl "\n"
#define pr pair<ll, ll>
#define ff first
#define ss second
#define all(x) x.begin(), x.end()
const int mod = 1e9+7;
void _p(ll a){cout<<a<<endl;}
void _p(string a){cout<<a<<endl;}
void _p(ld a) {cout<<a<<endl;}
template <class T>
void _p(vector<T> a){for(T val:a)cout<<val<<" ";cout<<endl;}
#define debug(x) cout<<#x<<" -> ";_p(x)
typedef tree<ll, null_type, less<ll>, rb_tree_tag, tree_order_statistics_node_update > ordered_set;
vector<pr> move8 = {{1, 0}, {1, 1}, {0, 1}, {-1, 1}, {-1, 0}, {-1, -1}, {0, -1}, {1, -1}};
vector<pr> move4 = {{1, 0}, {0, 1}, {-1, 0}, {0, -1}};
vector<pr> move2 = {{0, 1}, {1, 0}};
void solution();
int main() {
ios::sync_with_stdio(false);
cin.tie(nullptr);
cout.precision(4);
solution();
return 0;
}
vector<pair<ld, ld>> a;
ld L;
ll N;
bool isValid(ld d) {
d = d*d;
ld z = 1e-9;
for (int i = 0; i < N; i++) {
const ld r = sqrtl(d - a[i].ss*a[i].ss);
const ld p = a[i].ff - r;
const ld q = a[i].ff + r;
if (z >= p) z = max(z, q);
}
return z >= L;
}
void solution() {
cin >> N;
cin >> L;
a.resize(N);
for (int i = 0; i < N; i++) {
ld x, y; cin >> x >> y;
a[i] = {x, y};
}
ld ans = 0;
ld p = 0, q = 1.5e9;
while (q-p > 1e-3) {
const ld mid = (p + q)/2;
if (isValid(mid)) {
ans = mid;
q = mid;
} else{
p = mid;
}
}
cout << ans << endl;
}
