#include<bits/stdc++.h>
#define FILE "read"
#define eps 1e-10
#define INF 1e9
using namespace std;
const double pi=acos(-1);
struct Point{
	double x,y;
	Point(double a=0,double b=0):x(a),y(b){}
	inline void read(){scanf("%lf%lf",&x,&y);}
	inline void print(){printf("%.2lf %.2lf\n",x,y);}
	inline Point operator+(const Point &b){return Point(x+b.x,y+b.y);}
	inline Point operator-(const Point &b){return Point(x-b.x,y-b.y);}
	inline Point operator*(const double p){return Point(x*p,y*p);}
	inline Point operator/(const double p){return Point(x/p,y/p);}
	inline Point operator==(const Point &b){return fabs(x-b.x)<eps&&fabs(y-b.y)<eps;}
	inline Point operator< (const Point &b){return x<b.x||(x==b.x&&y<b.y);}
	inline double ang(){return atan2(y,x);}
}A,B,C;
struct Interval{
	double l,r;
	Interval(double a=0,double b=0):l(a),r(b){}
	inline bool In_Interval(double x){return x>=l&&x<=r;}
};
struct Circle{
	Point O; double r; 
	Circle(){}
	Circle(Point O,double r):O(O),r(r){}
	inline Point point(double rad){return Point(O.x+r*cos(rad),O.y+r*sin(rad));}
};
double t1,t2,L1,L2;
inline double Dot(Point A,Point B){return A.x*B.x+A.y*B.y;}
inline double Lenth(Point A){return sqrt(Dot(A,A));}
Interval Circle_Jiao(Circle c1,Circle c2){
	double a=c1.r;
	double b=c2.r;
	double c=Lenth(c1.O-c2.O);
	double temp=(c1.O-c2.O).ang();
	double delta=acos((a*a+c*c-b*b)/(2*a*c));
	return Interval(temp-delta,temp+delta);
}
bool Separate(Circle c1,Circle c2){
	return Lenth(c1.O-c2.O)>c1.r+c2.r+eps;
}
bool Contain(Circle c1,Circle c2){
	return Lenth(c1.O-c2.O)<fabs(c1.r-c2.r);
}
bool Interval_Jiao(Interval l1,Interval l2){
	return l1.In_Interval(l2.l)||l1.In_Interval(l2.r)||l2.In_Interval(l1.l)||l2.In_Interval(l1.r);
}
bool Judge(Circle c1,Circle c2,Circle c3){
	Interval l1=Circle_Jiao(c1,c2);
	Interval l2=Circle_Jiao(c1,c3);
	if(Interval_Jiao(l1,l2)) return 1;
	return 0;
}
bool check(double mid){
	Circle c1(A,mid);
	Circle c2(B,L1-mid);
	Circle c3(C,L2-Lenth(B-C)-mid);
	if(Separate(c1,c2)||Separate(c1,c3)||Separate(c2,c3)) return 0;
	if(Contain(c1,c2)||Contain(c1,c3)||Contain(c2,c3))  return 1;
	if(Judge(c1,c2,c3)||Judge(c2,c1,c3)||Judge(c3,c1,c2)) return 1;
	return 0;
}
void solve(){
	double l=0,r=min(L1,L2-Lenth(B-C));
	while(l+eps<r){
		double mid=(l+r)/2;
		if(check(mid)) l=mid;
		else r=mid;
	}
	printf("%.10lf\n",check(r)?r:l);
}
int main(){
	freopen(FILE".in","r",stdin);
	freopen(FILE".out","w",stdout);
	scanf("%lf%lf",&t2,&t1);
	A.read();  B.read();  C.read();
	L1=t1+Lenth(A-B);
	L2=t2+Lenth(A-C)+Lenth(B-C);
	if(L1>=Lenth(A-C)+Lenth(B-C)) printf("%.10lf\n",min(L1,L2));
	else solve();
	return 0;
}