#include <bits/stdc++.h>
using namespace std;
#define ll long long
#define pii pair<int, int>
#define ull unsigned ll
#define f first
#define s second
#define FOR(i,a,b) for (int i=(a); i<(b); ++i)
#define REP(i,n) FOR(i,0,n)
#define RREP(i,n) for (int i=(n-1); i>=0; --i)
#define REP1(i,n) FOR(i,1,n+1)
#define ALL(x) x.begin(),x.end()
#define SZ(x) (int)x.size()
#define SQ(x) (x)*(x)
#define MN(a,b) a = min(a,(__typeof__(a))(b))
#define MX(a,b) a = max(a,(__typeof__(a))(b))
#define pb push_back
#define SORT_UNIQUE(c) (sort(c.begin(),c.end()), c.resize(distance(c.begin(),unique(c.begin(),c.end()))))
#ifdef BALBIT
#define IOS()
#define bug(...) fprintf(stderr,"#%d (%s) = ",__LINE__,#__VA_ARGS__),_do(__VA_ARGS__);
template<typename T> void _do(T &&x){cerr<<x<<endl;}
template<typename T, typename ...S> void _do(T &&x, S &&...y){cerr<<x<<", ";_do(y...);}
#else
#define IOS() ios_base::sync_with_stdio(0);cin.tie(0);
#define endl '\n'
#define bug(...)
#endif
const int iinf = 1<<29;
const ll inf = 1ll<<60;
const ll mod = 1e9+7;
void GG(){cout<<"-1\n"; exit(0);}
ll mpow(ll a, ll n, ll mo = mod){ // a^n % mod
ll re=1;
while (n>0){
if (n&1) re = re*a %mo;
a = a*a %mo;
n>>=1;
}
return re;
}
ll inv (ll b, ll mo = mod){
if (b==1) return b;
return (mo-mo/b) * inv(mo%b) % mo;
}
const int maxn = 1e5+5;
struct pt{
double x, y;
bool operator < (const pt &b) const {
return tie(x,y) < tie(b.x,b.y);
}
pt operator + (const pt &b) const {
return {x+b.x,y+b.y};
}
pt operator - (const pt &b) const {
return {x-b.x,y-b.y};
}
pt operator * (const double d) const {
return {x*d,y*d};
}
pt operator / (const double d) const {
return {x/d,y/d};
}
double operator * (const pt &b) const {
return x*b.x + y*b.y;
}
double operator ^ (const pt &b) const { // Cross!
return x*b.y - y*b.x;
}
double len() {
return hypot(x,y);
}
pt(double xx=0, double yy=0): x(xx), y(yy){ }
};
struct line{
pt a, b, ab; // start and end points
line(pt _a, pt _b) {
a=_a; b=_b; ab = b-a;
}
double len(){
ab = b-a; return ab.len();
}
line(){}
};
double dist(pt &a, pt &b) {
return hypot(a.x-b.x,a.y-b.y);
}
pt proj(line p, pt q) {
// Point of minimum projection
if (p.ab.len() == 0) return p.a;
double k = (q-p.a)*(p.ab)/(SQ(p.ab.x) + SQ(p.ab.y)); // scaled factor of p
if (k<=0) return p.a; // on left
if (k >= 1) return p.b; // on right
return p.a + p.ab * k;
}
const double eps = 1e-7;
line wall[5];
const int MX = 4*200 + 8 + 10;
double d[MX][MX][2]; // Id 1, Id 2, parity
line fen[MX];
bool its(line p, line q) {
return ((q.a-p.a) ^ p.ab) * ((q.b-p.a) ^ p.ab) < 0 &&
((p.a-q.a) ^ q.ab) * ((p.b-q.a) ^ q.ab) < 0;
// If the ends of q are on different sides (opposite cross signs of p) and same applies for p
// Strictly less: touching is acceptable in case fence goes along the wall
}
bool ok(line p) {
REP(i,5) if (its(p,wall[i])) return 0;
return 1;
}
double dinf = 1e10;
line CUT = {{0,0},{1,7*11*13}};
signed main(){
IOS();
int n, s; cin>>n>>s;
// Build the walls
wall[0] = {{-s,s},{s,s}};
wall[1] = {{s,s},{s,-s}};
wall[2] = {{s,-s},{-s,-s}};
wall[3] = {{-s,-s},{-s,s}};
wall[4] = {{0,s},{0,-s}}; // To prevent diagonals of the square from skipping to each other
REP(i,n) {
int a, b, c, d; cin>>a>>b>>c>>d;
fen[i] = {{a,b},{c,d}};
}
REP(i,4) {
fen[i+n] = {wall[i].a,wall[i].a}; // Dummy lines for corners
}
bug((proj(fen[2],fen[3].a)-fen[3].a).len());
n+=4;
REP(i,n) REP(j,n) REP(k,2){
if (i==j && k==0) d[i][j][k] = 0;
else {
bool IJ = its(CUT,{fen[i].a, fen[j].a});
bool B;
// Assume the person is sitting at a for each fence
d[i][j][0]=d[i][j][1]=1e10;
line to;
// bug(d[i][j][B]);
to = {fen[i].a,proj(fen[j],fen[i].a)};
B = its(CUT,to) ^ its(CUT,line(fen[j].a,to.b));
if (ok(to)) MN(d[i][j][B],to.len() );
// First project from fen[i].a to fen[j], then walk back to fen[j].a
to = {fen[i].b,proj(fen[j],fen[i].b)};
B = its(CUT,to)^its(CUT,fen[i])^its(CUT,line(fen[j].a,to.b));
if (ok(to)) MN(d[i][j][B],to.len());
to = {fen[j].a,proj(fen[i],fen[j].a)};
B = its(CUT,to)^its(CUT,line(fen[i].a,to.b));
if (ok(to)) MN(d[i][j][B],to.len() );
to = {fen[j].b,proj(fen[i],fen[j].b)};
B = its(CUT,to)^its(CUT,fen[j])^its(CUT,line(fen[i].a,to.b));
if (ok(to)) MN(d[i][j][B],to.len() );
MN(d[j][i][0], d[i][j][0]); // It's the same going backwards
MN(d[j][i][1], d[i][j][1]);
bug(i,j,d[i][j][0],d[i][j][1]);
}
}
REP(k,n) REP(i,n) REP(j,n) REP(b1,2) REP(b2,2){
MN(d[i][j][b1^b2],d[i][k][b1] + d[k][j][b2]); // Floyd Warshall
}
bug("NOEFNOW");
double re = 1e10;
REP(i,n) REP(j,n) REP(k,2){
MN(re, d[i][i][1]);
bug(i,j,k,d[i][j][k]);
}
cout<<re<<endl;
}
