#include<iostream>
#include<vector>
#include<queue>
#include<deque>
#include<string>
#include<fstream>
#include<algorithm>
#include <iomanip>
#include<map>
#include <set>
#include <unordered_map>
#include <stack>
#include <unordered_set>
#include <cmath>
#define ll long long
#define For(i, n) for(ll i = 0; i < (ll)n; i++)
#define ffor(i, a, n) for(ll i = (ll)a; i < (ll)n; i++)
#define rfor(i, n) for(ll i = (ll)n; i >= (ll)0; i--)
#define rffor(i, a, n) for(ll i = (ll)n; i >= (ll)a; i--)
#define vec vector
#define ff first
#define ss second
#define pb push_back
#define shit short double
#define pii pair<long double, long double>
#define NEK 2147483640
#define mod 1000000007
#define mod2 1000000009
#define rsz resize
#define prv1 43
#define prv2 47
#define D 8
using namespace std;
long double bod(pii a, pii b) {
return (b.first * b.first + b.second * b.second - a.first * a.first - a.second * a.second) / (2 * (b.first - a.first));
}
long double dist(pii a, pii b) {
return sqrt(abs(a.ff - b.ff) * abs(a.ff - b.ff) + abs(a.ss - b.ss) * (abs(a.ss - b.ss)));
}
int main() {
ios_base::sync_with_stdio(false); cin.tie(NULL);
long double n, l;
cin >> n >> l;
vec<pii> p;
vec<long double> s;
For(i, n) {
long double x, y;
cin >> x >> y;
y = abs(y);
if (!p.empty()) {
if (p.back().ff == x) {
if (p.back().ss > y) {
p.pop_back();
p.push_back({ x, y });
}
continue;
}
}
p.push_back({ x, y });
}
For(i, p.size()) {
while (s.size() > 1 && bod(p[s[s.size() - 2]], p[s.back()]) > bod(p[s.back()], p[i])) s.pop_back();
s.push_back(i);
}
while (s.size() > 1 && bod(p[s[s.size() - 2]], p[s.back()]) > l) s.pop_back();
long double md = 0; bool prvy = false;
For(i, (s.size() - 1)) {
long double hod = bod(p[s[i]], p[s[i + 1]]);
if (hod < 0) continue;
if (prvy == false) {
md = dist(p[s[i]], { 0, 0 });
prvy = true;
}
md = max(md, dist(p[s[i]], { hod, 0 }));
md = max(md, dist(p[s[i + 1]], { hod, 0 }));
}
md = max(md, dist(p[s.back()], { l, 0 }));
cout << fixed << setprecision(3);
cout << md << endl;
return 0;
}
