/*
⡆⣐⢕⢕⢕⢕⢕⢕⢕⢕⠅⢗⢕⢕⢕⢕⢕⢕⢕⠕⠕⢕⢕⢕⢕⢕⢕⢕⢕⢕
⢐⢕⢕⢕⢕⢕⣕⢕⢕⠕⠁⢕⢕⢕⢕⢕⢕⢕⢕⠅⡄⢕⢕⢕⢕⢕⢕⢕⢕⢕
⢕⢕⢕⢕⢕⠅⢗⢕⠕⣠⠄⣗⢕⢕⠕⢕⢕⢕⠕⢠⣿⠐⢕⢕⢕⠑⢕⢕⠵⢕
⢕⢕⢕⢕⠁⢜⠕⢁⣴⣿⡇⢓⢕⢵⢐⢕⢕⠕⢁⣾⢿⣧⠑⢕⢕⠄⢑⢕⠅⢕
⢕⢕⠵⢁⠔⢁⣤⣤⣶⣶⣶⡐⣕⢽⠐⢕⠕⣡⣾⣶⣶⣶⣤⡁⢓⢕⠄⢑⢅⢑
⠍⣧⠄⣶⣾⣿⣿⣿⣿⣿⣿⣷⣔⢕⢄⢡⣾⣿⣿⣿⣿⣿⣿⣿⣦⡑⢕⢤⠱⢐
⢠⢕⠅⣾⣿⠋⢿⣿⣿⣿⠉⣿⣿⣷⣦⣶⣽⣿⣿⠈⣿⣿⣿⣿⠏⢹⣷⣷⡅⢐
⣔⢕⢥⢻⣿⡀⠈⠛⠛⠁⢠⣿⣿⣿⣿⣿⣿⣿⣿⡀⠈⠛⠛⠁⠄⣼⣿⣿⡇⢔
⢕⢕⢽⢸⢟⢟⢖⢖⢤⣶⡟⢻⣿⡿⠻⣿⣿⡟⢀⣿⣦⢤⢤⢔⢞⢿⢿⣿⠁⢕
⢕⢕⠅⣐⢕⢕⢕⢕⢕⣿⣿⡄⠛⢀⣦⠈⠛⢁⣼⣿⢗⢕⢕⢕⢕⢕⢕⡏⣘⢕
⢕⢕⠅⢓⣕⣕⣕⣕⣵⣿⣿⣿⣾⣿⣿⣿⣿⣿⣿⣿⣷⣕⢕⢕⢕⢕⡵⢀⢕⢕
⢑⢕⠃⡈⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⢃⢕⢕⢕
⣆⢕⠄⢱⣄⠛⢿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⣿⠿⢁⢕⢕⠕⢁
⣿⣦⡀⣿⣿⣷⣶⣬⣍⣛⣛⣛⡛⠿⠿⠿⠛⠛⢛⣛⣉⣭⣤⣂⢜⠕⢑⣡⣴⣿
*/
#include <bits/stdc++.h>
using namespace std;
typedef long long LL;
typedef long double LD;
#define MAX 100
#define pi acos(-1)
#define whatis(x) cout << #x << " is " << x << "\n";
#define all(x) x.begin(), x.end()
#define endl "\n"
#define DEB cout << "TESTING" NL
#define TESTS int test; cin>>test; for(int kase = 1 ; kase <= test ; kase++) solve(kase);
#define CASEOUT cout << "Case " << testcase << ": " <<
#define YESNO cout << (possible? "YES\n" : "NO\n");
// #define YES cout << "YES\n";
// #define NO cout << "NO\n";
#define int long long
#define pii pair<int,int>
LD distance(pair<LD, LD> a, pair<LD, LD> b)
{
return (a.first - b.first) * (a.first - b.first) + (a.second - b.second) * (a.second - b.second);
}
LD ternary(pair<LD, LD> a, pair<LD, LD> b)
{
LD low = a.first, high = b.first;
LD mid1, mid2, mid3;
do{
mid2 = low + (high - low)/2;
mid1 = low + (mid2 - low)/2;
mid3 = mid2 + (high - mid2)/2;
if(min(distance({mid1, 0}, a), distance({mid1, 0}, b)) < min(distance({mid3, 0}, a), distance({mid3, 0}, b)))
{
low = mid2;
}
else high = mid2;
} while(abs(mid2 - mid3) > 1e-4);
return mid2;
}
int solve(int testcase)
{
int n;
LD l;
cin >> n >> l;
vector <pair <LD, LD>> towers;
for(int i = 0; i < n; i++)
{
LD x, y;
cin >> x >> y;
if(!towers.size() || towers.back().first != x)
towers.push_back({x, y});
}
LD res = -1, start_point = LDBL_MAX, end_point = LDBL_MAX;
for(int i = 0 ; i < n ; i++)
{
start_point = min(start_point, distance({0, 0}, towers[i]));
end_point = min(end_point, distance({l, 0}, towers[i]));
}
for(int i = 0 ; i < towers.size()-1 ; i++)
{
LD point = ternary(towers[i], towers[i+1]);
if(point >= 0 && point <= l)
res = max({res, distance({point, 0}, towers[i]), distance({point, 0}, towers[i+1])});
}
res = max({res, sqrt(end_point), sqrt(start_point)});
cout << fixed << setprecision(6) << sqrt(res) << endl;
return 0;
}
signed main()
{
//freopen("input.txt", "r", stdin);
//freopen("output.txt", "w", stdout);
ios_base::sync_with_stdio(false);
cin.tie(NULL);
//cout.tie(NULL);
solve(0);
// TESTS
return 0;
}
