# include <bits/stdc++.h>
using namespace std;
const double eps=1e-8,INF=1e9;
struct Point
{
	double x,y;
	Point(double _x=0,double _y=0):x(_x),y(_y){}
	Point operator+(const Point &a)const{return Point(x+a.x,y+a.y);}
	Point operator-(const Point &a)const{return Point(x-a.x,y-a.y);}
	Point operator*(double k)const{return Point(x*k,y*k);}
	double operator*(const Point &a)const{return x*a.x+y*a.y;}
	double operator^(const Point &a)const{return x*a.y-y*a.x;}
	bool operator==(const Point &a)const{return fabs(x-a.x)<eps && fabs(y-a.y)<eps;}
};
struct Line
{
	Point A,B;
	Line(Point P=0):A(P),B(P){}
}L[110];
int n,S;
double dis[210][210];
void upd(double &a,double b){a=min(a,b);}
bool check(Point a){return max(fabs(a.x),fabs(a.y))>=S;}
bool onSeg(double x1,double x2,double x){return min(x1,x2)<=x && x<=max(x1,x2);}
bool onSeg(Point A,Point B,Point C){return onSeg(A.x,B.x,C.x) && onSeg(A.y,B.y,C.y);}
double sq(double x){return x*x;}
double dist2(Point A,Point B=0){return sq(A.x-B.x)+sq(A.y-B.y);}
double dist(Point A,Point B=0){return sqrt(dist2(A,B));}
bool check(Point A,Point B)
{
	if(!check(A) || !check(B)) return false;
	if(A==B) return true;
	double dx=A.x-B.x,dy=A.y-B.y;
	if(fabs(dx-dy)>eps)
	{
		double k=(A.x-A.y)/(dy-dx),x=A.x+k*dx,y=A.y+k*dy;
		if(onSeg(A,B,Point(x,y)) && !check(Point(x,y))) return false;
	}
	if(fabs(dx+dy)>eps)
	{
		double k=-(A.x+A.y)/(dx+dy),x=A.x+k*dx,y=A.y+k*dy;
		if(onSeg(A,B,Point(x,y)) && !check(Point(x,y))) return false;
	}
	return true;
}
int inter(Point A,Point B)
{
	if((A.x<0 && B.x<0) || (A.x>=0 && B.x>=0)) return 0;
	if(A.x>B.x) swap(A,B);
	return ((Point()-A)^(B-A))>0;
}
void W(int i,int j)
{
	auto U=[&](int t,double d){for(int k=0;k<2;k++) upd(dis[2*i-k][2*j-(k^t)],d);};
	auto calc=[&](Point A,Point B){return inter(L[i].A,A)^inter(A,B)^inter(B,L[j].A);};
	for(Point A:{L[i].A,L[i].B})
		for(Point B:{L[j].A,L[j].B})
			if(check(A,B)) U(calc(A,B),dist(A,B));
	if(L[i].A==L[i].B || L[j].A==L[j].B) return;
	for(Point A:{L[i].A,L[i].B})
	{
		Point P0=L[j].A,a=A-P0,b=L[j].B-P0,P=P0+b*(a*b/dist2(b));
		if(onSeg(L[j].A,L[j].B,P) && check(A,P)) U(calc(A,P),dist(A,P));
	}
	for(Point A:{L[j].A,L[j].B})
	{
		Point P0=L[i].A,a=A-P0,b=L[i].B-P0,P=P0+b*(a*b/dist2(b));
		if(onSeg(L[i].A,L[i].B,P) && check(A,P)) U(calc(P,A),dist(A,P));
	}
}
int main()
{
	cin>>n>>S;
	for(int i=1;i<=n;i++) scanf("%lf%lf%lf%lf",&L[i].A.x,&L[i].A.y,&L[i].B.x,&L[i].B.y);
	for(int x:{-S,S})
		for(int y:{-S,S})
			L[++n]=Line(Point(x,y));
	for(int i=1;i<=2*n;i++) fill(dis[i]+1,dis[i]+2*n+1,INF);
	for(int i=1;i<=n;i++)
		for(int j=1;j<=n;j++)
			W(i,j);
	for(int k=1;k<=2*n;k++)
		for(int i=1;i<=2*n;i++)
			for(int j=1;j<=2*n;j++)
				upd(dis[i][j],dis[i][k]+dis[k][j]);
	double ans=INF;
	for(int i=1;i<=n;i++) upd(ans,dis[2*i-1][2*i]);
	printf("%.10lf\n",ans);
	return 0;
}