// Knapsack DP is harder than FFT.
#include<bits/stdc++.h>
using namespace std;
typedef long long ll; typedef pair<int,int> pii;
#define ff first
#define ss second
#define pb emplace_back
#define AI(x) begin(x),end(x)
#ifdef OWO
#define debug(args...) SDF(#args, args)
#define OIU(args...) ostream& operator<<(ostream&O,args)
#define LKJ(S,B,E,F) template<class...T>OIU(S<T...>s){O<<B;int c=0;for(auto i:s)O<<(c++?", ":"")<<F;return O<<E;}
LKJ(vector,'[',']',i)LKJ(deque,'[',']',i)LKJ(set,'{','}',i)LKJ(multiset,'{','}',i)LKJ(unordered_set,'{','}',i)LKJ(map,'{','}',i.ff<<':'<<i.ss)LKJ(unordered_map,'{','}',i.ff<<':'<<i.ss)
template<class...T>void SDF(const char* s,T...a){int c=sizeof...(T);if(!c){cerr<<"\033[1;32mvoid\033[0m\n";return;}(cerr<<"\033[1;32m("<<s<<") = (",...,(cerr<<a<<(--c?", ":")\033[0m\n")));}
template<class T,size_t N>OIU(array<T,N>a){return O<<vector<T>(AI(a));}template<class...T>OIU(pair<T...>p){return O<<'('<<p.ff<<','<<p.ss<<')';}template<class...T>OIU(tuple<T...>t){return O<<'(',apply([&O](T...s){int c=0;(...,(O<<(c++?", ":"")<<s));},t),O<<')';}
#else
#define debug(...) ((void)0)
#endif
const double INF = 1e18;
const double eps = 1e-9;
int sign(double d) { return (d >= eps) - (d <= eps); }
struct Vec {
double x, y;
Vec () = default;
Vec (const double& _x, const double& _y): x(_x), y(_y) {}
const Vec operator + (const Vec& o) const { return Vec(x + o.x, y + o.y); }
const Vec operator - (const Vec& o) const { return Vec(x - o.x, y - o.y); }
const Vec operator * (const double& v) const { return Vec(x * v, y * v); }
const double operator * (const Vec& o) const { return x * o.x + y * o.y; }
const double operator ^ (const Vec& o) const { return x * o.y - y * o.x; }
const double abs2 () const { return x * x + y * y; }
const double abs () const { return sqrt(x * x + y * y); }
};
struct Seg {
Vec a, b;
Seg () = default;
Seg (const Vec& _a, const Vec& _b): a(_a), b(_b) {}
Seg (const int& _a, const int& _b, const int& _c, const int& _d)
: a(_a, _b), b(_c, _d) {}
};
const int ori(const Vec& o, const Vec& a, const Vec& b)
{ return sign((a - o) ^ (b - o)); }
const bool intersect(const Seg& a, const Seg& b) {
return ori(a.a, a.b, b.a) * ori(a.a, a.b, b.b) < 0
and ori(b.a, b.b, a.a) * ori(b.a, b.b, a.b) < 0;
}
const bool has_T(const Vec& v, const Seg& s) {
return sign((v - s.a) * (s.b - s.a)) > 0
and sign((v - s.b) * (s.a - s.b)) > 0;
}
const Vec T_point(const Vec& v, const Seg& s) {
const Vec AB = s.b - s.a;
const Vec AV = v - s.a;
return s.a + AB * ((AB * AV) / AB.abs2());
}
Seg diaA, diaB, uwu;
double dis[2];
void add_edge(const Vec& a, const Vec& b, const Vec& c, const Vec& d) {
Seg ab(a, b), bc(b, c), cd(c, d);
if (intersect(bc, diaA) or intersect(bc, diaB))
return;
bool owo = intersect(ab, uwu) xor intersect(bc, uwu) xor intersect(cd, uwu);
dis[owo] = min(dis[owo], (c - b).abs());
}
void solve(const Seg& a, const Seg& b) {
dis[0] = dis[1] = INF;
add_edge(a.a, a.a, b.b, b.a);
add_edge(a.a, a.b, b.b, b.a);
add_edge(a.a, a.a, b.a, b.a);
add_edge(a.a, a.b, b.a, b.a);
if (has_T(a.a, b)) add_edge(a.a, a.a, T_point(a.a, b), b.a);
if (has_T(a.b, b)) add_edge(a.a, a.b, T_point(a.b, b), b.a);
if (has_T(b.a, a)) add_edge(a.a, T_point(b.a, a), b.a, b.a);
if (has_T(b.b, a)) add_edge(a.a, T_point(b.b, a), b.b, b.a);
}
signed main() {
ios_base::sync_with_stdio(0); cin.tie(0); cout.tie(0);
int N, S; cin >> N >> S;
vector<Seg> segs;
for (int A, B, C, D, i = 0; i < N; ++i) {
cin >> A >> B >> C >> D;
segs.emplace_back(A, B, C, D);
}
N = N + 4;
for (const int& x: {S, -S})
for (const int& y: {S, -S})
segs.emplace_back(x, y, x, y);
diaA = Seg(S, S, -S, -S);
diaB = Seg(S, -S, -S, S);
uwu = Seg(0, 0, 1, 3000);
vector<vector<double>> dp(N * 2, vector<double>(N * 2, INF));
for (int i = 0; i < N; ++i)
for (int j = 0; j < N; ++j) {
solve(segs[i], segs[j]);
dp[i * 2][j * 2] = dp[i * 2 + 1][j * 2 + 1] = dis[0];
dp[i * 2 + 1][j * 2] = dp[i * 2][j * 2 + 1] = dis[1];
}
for (int k = 0; k < N * 2; ++k)
for (int i = 0; i < N * 2; ++i) if (dp[i][k] != INF)
for (int j = 0; j < N * 2; ++j) if (dp[k][j] != INF)
dp[i][j] = min(dp[i][j], dp[i][k] + dp[k][j]);
double ans = INF;
for (int i = 0; i < N; ++i)
ans = min(ans, dp[i * 2][i * 2 + 1]);
cout << setprecision(9) << fixed << ans << '\n';
return 0;
}
