//#pragma GCC optimize("O3,unroll-loops,Ofast")
//#pragma GCC target("avx2,bmi,bmi2,popcnt,lzcnt")
#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;
#define MAX 200005
#define pb push_back
#define mp make_pair
#define int long long
#define f first
#define s second
#define vi vector<int>
#define pii pair<int,int>
#define si set<int>
#define vpii vector<pair<int,int>>
const int mod = 1e9+7;
const int INF = 1e18;
// myMap.begin()->first : key
// myMap.begin()->second : value
//#define double double
int epow(int a,int b){int ans=1;while(b){if(b&1) ans*=a;a*=a;b>>=1;a%=mod;ans%=mod;}return ans%=mod;}
int gcd(int a,int b) {if(a<b)swap(a,b);while(b){int tmp=b;b=a%b;a=tmp;}return a;}
int mul(long long a,long long b){return ((a%mod)*(b%mod))%mod;}
int sum(long long a,long long b){return ((a%mod)+(b%mod))%mod;}
// typedef tree<int,null_type,less<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_set;
// typedef
// tree<int,null_type,less_equal<int>,rb_tree_tag,tree_order_statistics_node_update>ordered_multiset;
void solve(){
int n,L; cin>>n>>L;
vpii v(n+2); for(int i=1;i<=n;i++) cin>>v[i].f>>v[i].s;
double l=0,r=2e9;
while(r-l>1e-6){
vector<pair<double,double>> arr;
double mid=(l+r)/2.0;
double mx=0.0;
for(int i=1;i<=n;i++){
if(v[i].s*v[i].s>mid*mid) continue;
double a = sqrt(mid*mid-v[i].s*v[i].s);
double l=v[i].f-a,r=v[i].f+a;
if(l<=mx) mx=max(mx,r);
}
if(mx<(double)L) l=mid;
else r=mid;
}
cout << fixed << setprecision(6);
cout<<l<<endl;
return;
}
int32_t main(/*int32_t argc, char* argv[]*/){
ios_base::sync_with_stdio(0); cin.tie(0);
// freopen("dining.in", "r", stdin);
// freopen("dining.out", "w", stdout);
int t=1;
// cin >> t;
while (t--) solve();
return 0;
}
