/*Author: KawakiMeido*/
#include <bits/stdc++.h>
#define pb push_back
#define endl "\n"
#define ll long long
#define int long long
#define all(x) (x).begin(),(x).end()
#define pii pair<int,int>
#define fi first
#define se second
using namespace std;
/*Constants*/
const int N = 2e5+10;
const int INF = 1e9+7;
const long long LLINF = 1e18+3;
/*TestCases*/
int test=1;
void solve();
void TestCases(bool v){
if (v) cin >> test;
while(test--) solve();
}
/*Global Variables*/
int n;
int L;
vector<pii> a,v;
bool check(long double delta){
long double x = 0;
for (int i=0; i<(int)v.size(); i++){
if (delta<v[i].se) continue;
long double sus = sqrt((long double)(delta*delta - v[i].se*v[i].se));
long double l = (long double) v[i].fi - sus;
long double r = (long double) v[i].fi + sus;
if (l<=x){
x = max(x,r);
}
}
if (x>=L) return true;
else return false;
}
/*Solution*/
void solve(){
cin >> n >> L;
for (int i=1; i<=n; i++){
int x,y; cin >> x >> y;
a.push_back({x,abs(y)});
}
sort(all(a));
for (int i=0; i<n; i++){
// if (!v.empty() && a[i].se > v.back().se){
// int delta = min(v.back().se,a[i].se);
// long double sus1 = sqrt((long double)(delta*delta - v.back().se*v.back().se));
// long double sus2 = sqrt((long double)(delta*delta - a[i].se*a[i].se));
// long double l1 = (long double) v.back().fi - sus1;
// long double r1 = (long double) v.back().fi + sus1;
// long double l2 = (long double) a[i].fi - sus2;
// long double r2 = (long double) a[i].fi + sus2;
//
// if (r1>=r2) continue;
// }
// while (!v.empty()){
// int delta = min(v.back().se,a[i].se);
// long double sus1 = sqrt((long double)(delta*delta - v.back().se*v.back().se));
// long double sus2 = sqrt((long double)(delta*delta - a[i].se*a[i].se));
// long double l1 = (long double) v.back().fi - sus1;
// long double r1 = (long double) v.back().fi + sus1;
// long double l2 = (long double) a[i].fi - sus2;
// long double r2 = (long double) a[i].fi + sus2;
//
// if (l1<l2) break;
//
// v.pop_back();
// }
v.push_back({a[i].fi,a[i].se});
}
long double l = 0, r = (int) 2e9;
long double ans = r;
for (int i=1; i<=50; i++){
long double mid = (l+r)/2;
if (check(mid)){
ans = mid;
r = mid;
}
else{
l = mid;
}
}
cout << fixed << setprecision(6) << ans << endl;
}
/*Driver Code*/
signed main(){
ios_base::sync_with_stdio(0);
cin.tie(0);
TestCases(0);
return 0;
}
