#include <bits/stdc++.h>
using namespace std;
#define X first
#define Y second
#define mp make_pair
#define pb push_back
#define Debug(...) fprintf(stderr, __VA_ARGS__)
typedef long long LL;
typedef long double LD;
typedef unsigned int uint;
typedef pair <int, int> pii;
typedef unsigned long long uLL;
template <typename T> inline void Read(T &x) {
char c = getchar();
bool f = false;
for (x = 0; !isdigit(c); c = getchar()) {
if (c == '-') {
f = true;
}
}
for (; isdigit(c); c = getchar()) {
x = x * 10 + c - '0';
}
if (f) {
x = -x;
}
}
template <typename T> inline bool CheckMax(T &a, const T &b) {
return a < b ? a = b, true : false;
}
template <typename T> inline bool CheckMin(T &a, const T &b) {
return a > b ? a = b, true : false;
}
const int N = 420;
const double eps = 1e-6;
const double inf = 1e9;
inline int Sgn(double x) {
return fabs(x) < eps ? 0 : x > 0 ? 1 : -1;
}
inline int Cmp(double x, double y) {
return Sgn(x - y);
}
inline bool Mid(double l, double r, double mid) {
return Cmp(l, mid) * Cmp(r, mid) <= 0;
}
struct Point {
double x, y;
Point(double _x = 0, double _y = 0) {
x = _x, y = _y;
}
Point operator + (const Point &b) const {
return Point(x + b.x, y + b.y);
}
Point operator - (const Point &b) const {
return Point(x - b.x, y - b.y);
}
Point operator * (const double &b) const {
return Point(x * b, y * b);
}
Point operator / (const double &b) const {
return Point(x / b, y / b);
}
double operator * (const Point &b) const {
return x * b.x + y * b.y;
}
double operator ^ (const Point &b) const {
return x * b.y - y * b.x;
}
bool operator == (const Point &b) const {
return !Cmp(x, b.x) && !Cmp(y, b.y);
}
bool operator != (const Point &b) const {
return Cmp(x, b.x) || Cmp(y, b.y);
}
inline double Len() {
return x * x + y * y;
}
} s(0, 0), t(1, 1000), r[4], p[N], q[N];
double ans, dis[N][N];
int n, m;
inline double Dis(Point x, Point y) {
return sqrt((x - y).Len());
}
inline bool Mid(Point l, Point r, Point mid) {
return Mid(l.x, r.x, mid.x) && Mid(l.y, r.y, mid.y);
}
inline Point Projection(Point p, Point q, Point x) {
Point delta = q - p;
return p + delta * ((x - p) * delta / delta.Len());
}
inline bool IntersectInterval(double l1, double r1, double l2, double r2) {
if (l1 > r1) {
swap(l1, r1);
}
if (l2 > r2) {
swap(l2, r2);
}
return Cmp(r1, l2) > 0 && Cmp(r2, l1) > 0;
}
inline bool IntersectSegment(Point l1, Point r1, Point l2, Point r2) {
if (!IntersectInterval(l1.x, r1.x, l2.x, r2.x) || !IntersectInterval(l1.y, r1.y, l2.y, r2.y)) {
return false;
}
return Sgn((l2 - l1) ^ (r2 - l1)) * Sgn((l2 - r1) ^ (r2 - r1)) < 0 && Sgn((l1 - l2) ^ (r1 - l2)) * Sgn((l1 - r2) ^ (r1 - r2)) < 0;
}
inline bool Check(Point x, Point y) {
for (int i = 0; i < 4; ++i) {
if (IntersectSegment(x, y, r[i], r[i + 1 & 3])) {
return false;
}
}
Point z = (x + y) / 2;
if (z.x > -m && z.x < m && z.y > -m && z.y < m) {
return false;
}
return true;
}
inline void AddEdge(int x, int y, double d) {
if (IntersectSegment(x <= n ? p[x] : q[x - n], y <= n ? p[y] : q[y - n], s, t)) {
CheckMin(dis[x][y + (n << 1)], d);
CheckMin(dis[y][x + (n << 1)], d);
CheckMin(dis[y + (n << 1)][x], d);
CheckMin(dis[x + (n << 1)][y], d);
} else {
CheckMin(dis[x][y], d);
CheckMin(dis[y][x], d);
CheckMin(dis[x + (n << 1)][y + (n << 1)], d);
CheckMin(dis[y + (n << 1)][x + (n << 1)], d);
}
}
inline void AddEdge(int x, int y, double d, bool f) {
if (f) {
CheckMin(dis[x][y + (n << 1)], d);
CheckMin(dis[y][x + (n << 1)], d);
CheckMin(dis[y + (n << 1)][x], d);
CheckMin(dis[x + (n << 1)][y], d);
} else {
CheckMin(dis[x][y], d);
CheckMin(dis[y][x], d);
CheckMin(dis[x + (n << 1)][y + (n << 1)], d);
CheckMin(dis[y + (n << 1)][x + (n << 1)], d);
}
}
int main() {
#ifdef wxh010910
freopen("d.in", "r", stdin);
#endif
Read(n), Read(m), ans = m << 3;
for (int i = 1; i <= n; ++i) {
Read(p[i].x), Read(p[i].y), Read(q[i].x), Read(q[i].y);
}
r[0] = Point(m, m), r[1] = Point(m, -m), r[2] = Point(-m, -m), r[3] = Point(-m, m);
for (int i = 0; i < 4; ++i) {
++n, p[n] = q[n] = r[i];
}
for (int i = 1; i <= n << 2; ++i) {
for (int j = 1; j <= n << 2; ++j) {
dis[i][j] = i == j ? 0 : inf;
}
}
for (int i = 1; i <= n; ++i) {
AddEdge(i, i + n, 0);
for (int j = 1; j < i; ++j) {
if (Check(p[i], p[j])) {
AddEdge(i, j, Dis(p[i], p[j]));
}
if (Check(p[i], q[j])) {
AddEdge(i, j + n, Dis(p[i], q[j]));
}
if (Check(q[i], p[j])) {
AddEdge(i + n, j, Dis(q[i], p[j]));
}
if (Check(q[i], q[j])) {
AddEdge(i + n, j + n, Dis(q[i], q[j]));
}
Point tmp;
tmp = Projection(p[j], q[j], p[i]);
if (Mid(p[j], q[j], tmp) && Check(p[i], tmp)) {
AddEdge(i, j, Dis(p[i], tmp), IntersectSegment(p[i], tmp, s, t) ^ IntersectSegment(p[j], tmp, s, t));
AddEdge(i, j + n, Dis(p[i], tmp), IntersectSegment(p[i], tmp, s, t) ^ IntersectSegment(q[j], tmp, s, t));
}
tmp = Projection(p[j], q[j], q[i]);
if (Mid(p[j], q[j], tmp) && Check(q[i], tmp)) {
AddEdge(i + n, j, Dis(q[i], tmp), IntersectSegment(q[i], tmp, s, t) ^ IntersectSegment(p[j], tmp, s, t));
AddEdge(i + n, j + n, Dis(q[i], tmp), IntersectSegment(q[i], tmp, s, t) ^ IntersectSegment(q[j], tmp, s, t));
}
swap(i, j);
tmp = Projection(p[j], q[j], p[i]);
if (Mid(p[j], q[j], tmp) && Check(p[i], tmp)) {
AddEdge(i, j, Dis(p[i], tmp), IntersectSegment(p[i], tmp, s, t) ^ IntersectSegment(p[j], tmp, s, t));
AddEdge(i, j + n, Dis(p[i], tmp), IntersectSegment(p[i], tmp, s, t) ^ IntersectSegment(q[j], tmp, s, t));
}
tmp = Projection(p[j], q[j], q[i]);
if (Mid(p[j], q[j], tmp) && Check(q[i], tmp)) {
AddEdge(i + n, j, Dis(q[i], tmp), IntersectSegment(q[i], tmp, s, t) ^ IntersectSegment(p[j], tmp, s, t));
AddEdge(i + n, j + n, Dis(q[i], tmp), IntersectSegment(q[i], tmp, s, t) ^ IntersectSegment(q[j], tmp, s, t));
}
swap(i, j);
}
}
for (int k = 1; k <= n << 2; ++k) {
for (int i = 1; i <= n << 2; ++i) {
for (int j = 1; j <= n << 2; ++j) {
CheckMin(dis[i][j], dis[i][k] + dis[k][j]);
}
}
}
for (int i = 1; i <= n << 1; ++i) {
CheckMin(ans, dis[i][i + (n << 1)]);
}
printf("%lf\n", ans);
#ifdef wxh010910
Debug("My Time: %.3lfms\n", (double)clock() / CLOCKS_PER_SEC);
#endif
return 0;
}
