#include <bits/stdc++.h>
using namespace std;
#define fastio() ios::sync_with_stdio(false); cin.tie(NULL)
#define ll long long
#define endl '\n'
long double get_inter(pair<ll, ll> t1, pair<ll, ll> t2) {
long double result = (long double)t2.second * t2.second - (long double)t1.second * t1.second;
long double result2 = t2.first - t1.first;
long double result3 = t2.first + t1.first;
return (result / result2 + result3) / 2.0;
}
int main() {
fastio();
int n, l;
cin >> n >> l;
vector<pair<long long, long long>> towers(n);
for (int i = 0; i < n; i++) {
cin >> towers[i].first >> towers[i].second;
}
stack<int> st;
stack<long double> inter_st;
for (int i = 0; i < n; i++) {
while (st.size() >= 2) {
long double new_inter = get_inter(towers[st.top()], towers[i]);
if (new_inter <= inter_st.top()) {
st.pop();
inter_st.pop();
} else {
break;
}
}
if (!st.empty()) {
inter_st.push(get_inter(towers[st.top()], towers[i]));
}
st.push(i);
}
vector<int> final_towers;
vector<long double> final_inters;
while (!st.empty()) {
final_towers.push_back(st.top());
st.pop();
}
while (!inter_st.empty()) {
final_inters.push_back(inter_st.top());
inter_st.pop();
}
reverse(final_towers.begin(), final_towers.end());
reverse(final_inters.begin(), final_inters.end());
long double max_ = 0;
max_ = max(max_, (long double)sqrtl((long double)towers[final_towers[0]].first * towers[final_towers[0]].first + (long double)towers[final_towers[0]].second * towers[final_towers[0]].second));
max_ = max(max_, (long double)sqrtl((long double)(l - towers[final_towers.back()].first) * (l - towers[final_towers.back()].first) + (long double)towers[final_towers.back()].second * towers[final_towers.back()].second));
for (int i = 0; i < final_inters.size(); i++) {
long double x = final_inters[i];
if (x < 0) x = 0;
if (x > l) x = l;
long double d = sqrtl((x - towers[final_towers[i]].first) * (x - towers[final_towers[i]].first) + (long double)towers[final_towers[i]].second * towers[final_towers[i]].second);
max_ = max(max_, d);
}
cout << fixed << setprecision(4) << max_ << endl;
return 0;
}
