#include <bits/stdc++.h>
using namespace std;
const long double eps = 1e-10;
int dcmp(long double x) {
  if (fabs(x) < eps) return 0;
  return x < 0 ? -1 : 1;
}
long double sqr(long double x) { return x * x; }
struct Point {
  long double x, y;
  Point(long double x = 0, long double y = 0) : x(x), y(y) {}
  void read() { cin >> x >> y; }
};
Point operator-(const Point& A, const Point& B) {
  return Point(A.x - B.x, A.y - B.y);
}
bool operator==(const Point& A, const Point& B) {
  return dcmp(A.x - B.x) == 0 && dcmp(A.y - B.x) == 0;
}
long double Dot(const Point& A, const Point& B) {
  return A.x * B.x + A.y * B.y;
}
long double Length(const Point& A) { return sqrt(Dot(A, A)); }
long double angle(const Point& A) { return atan2(A.y, A.x); }
struct Circle {
  Point c;
  long double r;
  Circle() {}
  Circle(Point c, long double r) : c(c), r(r) {}
  Point point(long double a) {
    return Point(c.x + cos(a) * r, c.y + sin(a) * r);
  }
};
long double t1, t2, T1, T2;
Point p[3];
Circle o[3];
vector<Point> inter;
bool OnCircle(Point p, Circle C) { return dcmp(Length(p - C.c) - C.r) == 0; }
bool getCircleIntersection(Circle C1, Circle C2) {
  long double &r1 = C1.r, &r2 = C2.r;
  long double &x1 = C1.c.x, &x2 = C2.c.x, &y1 = C1.c.y, &y2 = C2.c.y;
  long double d = Length(C1.c - C2.c);
  if (dcmp(fabs(r1 - r2) - d) > 0) return true;
  if (dcmp(r1 + r2 - d) < 0) return false;
  long double d2 = Dot(C1.c - C2.c, C1.c - C2.c);
  long double a = r1 * (x1 - x2) * 2, b = r1 * (y1 - y2) * 2,
              c = r2 * r2 - r1 * r1 - d * d;
  long double p = a * a + b * b, q = -a * c * 2, r = c * c - b * b;
  long double cosa, sina, cosb, sinb;
  if (dcmp(d - (r1 + r2)) == 0 || dcmp(d - fabs(r1 - r2)) == 0) {
    cosa = -q / p / 2;
    sina = sqrt(1 - sqr(cosa));
    Point p(x1 + C1.r * cosa, y1 + C1.r * sina);
    if (!OnCircle(p, C2)) p.y = y1 - C1.r * sina;
    inter.push_back(p);
    return true;
  }
  long double delta = sqrt(q * q - p * r * 4);
  cosa = (delta - q) / p / 2;
  cosb = (-delta - q) / p / 2;
  sina = sqrt(1 - sqr(cosa));
  sinb = sqrt(1 - sqr(cosb));
  Point p1(x1 + C1.r * cosa, y1 + C1.r * sina);
  Point p2(x1 + C1.r * cosb, y1 + C1.r * sinb);
  if (!OnCircle(p1, C2)) p1.y = y1 - C1.r * sina;
  if (!OnCircle(p2, C2)) p2.y = y1 - C1.r * sinb;
  if (p1 == p2) p1.y = y1 - C1.r * sina;
  inter.push_back(p1);
  inter.push_back(p2);
  return true;
}
bool Include(Circle C1, Circle C2) {
  long double d = Length(C1.c - C2.c);
  if (dcmp(fabs(C1.r - C2.r) - d) > 0) return true;
  return false;
}
bool InAllCircle(const Point& t) {
  for (int i = 0; i < 3; i++) {
    long double d = Length(t - o[i].c);
    if (dcmp(d - o[i].r) > 0) return false;
  }
  return true;
}
bool check() {
  inter.clear();
  for (int i = 0; i < 3; i++)
    for (int j = i + 1; j < 3; j++)
      if (!getCircleIntersection(o[i], o[j])) return false;
  for (int i = 0; i < 3; i++)
    for (int j = i + 1; j < 3; j++)
      if (Include(o[i], o[j])) return true;
  for (Point t : inter)
    if (InAllCircle(t)) return true;
  return false;
}
int main() {
  cout << fixed << setprecision(15);
  cin >> t1 >> t2;
  for (int i = 0; i < 3; i++) p[i].read();
  long double AB = Length(p[1] - p[0]);
  long double AC = Length(p[2] - p[0]);
  long double BC = Length(p[2] - p[1]);
  T1 = AC + BC + t1;
  T2 = AB + t2;
  if (dcmp(T2 - AC - BC) >= 0) {
    cout << min(T1, T2) << endl;
    return 0;
  }
  long double L = 0, R = min(T1 - BC, T2);
  for (int i = 0; i < 100; i++) {
    long double mid = (L + R) / 2.0;
    o[0] = Circle(p[0], mid);
    o[1] = Circle(p[1], T2 - mid);
    o[2] = Circle(p[2], T1 - BC - mid);
    if (check())
      L = mid;
    else
      R = mid;
  }
  cout << L << endl;
  return 0;
}
