//In The Name Of ALLAH!
// #pragma GCC optimize("O3")
#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ll long long
#define ld double
#define endl '\n'
#define pb push_back
#define pf push_front
#define Zemur007 ios_base::sync_with_stdio(false); cin.tie(NULL); cout.tie(NULL);
#define bpc __builtin_popcountll
#define btz __builtin_ctzll
#define all(x) x.begin() , x.end()
#define allr(x) x.rbegin() , x.rend()
#define F first
#define S second
#define pii pair<int , int>
#define pll pair<ll , ll>
#define turtle tuple<ll , ll , ll>
#define pss pair<string , string>
#define YES cout << "YES" << endl;
#define NO cout << "NO" << endl;
#define indexed_set tree<pll , null_type , less<pll> , rb_tree_tag , tree_order_statistics_node_update>
const ll sz = 1e6 + 5 , INF = 1e18 , MOD = 998244353;
pair<ld , ld> a[sz];
ll mask , i , j , k;
void solve(){
ll n , L; cin >> n >> L;
for(i = 1 ; i <= n ; i++) cin >> a[i].F >> a[i].S;
ld l = 1, r = 1.5e9 , mid , best = r;
while(r - l > 1e-3){
mid = (l + r) / 2.0;
double last = 0.0;
for(i = 1 ; i <= n ; i++){
double d = sqrt(mid * mid - a[i].S * a[i].S);
double start = a[i].F - d , end = a[i].F + d;
if(start <= last) last = max(last , end);
if(last >= L) break;
}
if(last >= L){
best = mid;
r = mid;
}
else l = mid;
}
cout << fixed << setprecision(3) << best << endl;
}
//A Hero can be anyone.Even a man doing something as simple and reassuring as putting his coat around young boy's shoulders to let him know that world hadn't ended yet
signed main(){
Zemur007;
// open();
ll t = 1;
// cin >> t;
while(t--){
solve();
}
// for(ll testcase = 1 ; testcase <= t ; testcase++){
// cout << "Case " << testcase << ":" << endl;
// solve();
// }
}
