#include <bits/stdc++.h>
using namespace std;
#define int long long
#define rep(i,n) for(int (i)=0;(i)<(n);(i)++)
#define rrep(i,n) for(int (i)=((n)-1);(i)>=0;(i)--)
#define itn int
#define miele(v) min_element(v.begin(), v.end())
#define maele(v) max_element(v.begin(), v.end())
#define SUM(v) accumulate(v.begin(), v.end(), 0LL)
#define lb(a, key) lower_bound(a.begin(),a.end(),key)
#define ub(a, key) upper_bound(a.begin(),a.end(),key)
#define COUNT(a, key) count(a.begin(), a.end(), key) 
#define BITCOUNT(x) __builtin_popcount(x)
#define pb push_back
#define all(x) (x).begin(),(x).end()
#define F first
#define S second
using P = pair <int,long double>;
using WeightedGraph = vector<vector <P>>;
using UnWeightedGraph = vector<vector<int>>;
using Real = long double;
using Point = complex<Real>; //Point and Vector2d is the same!
using Vector2d = complex<Real>;
const long long INF = 1LL << 60;
const int MOD = 1000000007;
const long double EPS = 1e-12;
const long double PI=3.14159265358979323846;
template <typename T> 
int getIndexOfLowerBound(vector <T> &v, T x){
    return lower_bound(v.begin(),v.end(),x)-v.begin();
}
template <typename T> 
int getIndexOfUpperBound(vector <T> &v, T x){
    return upper_bound(v.begin(),v.end(),x)-v.begin();
}
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
#define DUMPOUT cerr
#define repi(itr, ds) for (auto itr = ds.begin(); itr != ds.end(); itr++)
istream &operator>>(istream &is, Point &p) {
    Real a, b; is >> a >> b; p = Point(a, b); return is;
}
template <typename T, typename U>
istream &operator>>(istream &is, pair<T,U> &p_var) {
    is >> p_var.first >> p_var.second;
    return is;
}
template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec) is >> x;
    return is;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, pair<T, U> &pair_var) {
    DUMPOUT<<'{';
    os << pair_var.first;
    DUMPOUT<<',';
    os << " "<< pair_var.second;
    DUMPOUT<<'}';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<T> &vec) {
    DUMPOUT<<'[';
    for (int i = 0; i < vec.size(); i++) 
    os << vec[i] << (i + 1 == vec.size() ? "" : " ");
    DUMPOUT<<']';
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, vector<vector<T>> &df) {
  for (auto& vec : df) os<<vec;
  return os;
}
template <typename T, typename U>
ostream &operator<<(ostream &os, map<T, U> &map_var) {
    DUMPOUT << "{";
    repi(itr, map_var) {
        os << *itr;
        itr++;
        if (itr != map_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
template <typename T>
ostream &operator<<(ostream &os, set<T> &set_var) {
    DUMPOUT << "{";
    repi(itr, set_var) {
        os << *itr;
        itr++;
        if (itr != set_var.end()) DUMPOUT << ", ";
        itr--;
    }
    DUMPOUT << "}";
    return os;
}
void print() {cout << endl;}
template <class Head, class... Tail>
void print(Head&& head, Tail&&... tail) {
  cout << head;
  if (sizeof...(tail) != 0) cout << " ";
  print(forward<Tail>(tail)...);
}
void dump_func() {DUMPOUT << '#'<<endl;}
template <typename Head, typename... Tail>
void dump_func(Head &&head, Tail &&... tail) {
    DUMPOUT << head;
    if (sizeof...(Tail) > 0) DUMPOUT << ", ";
    dump_func(std::move(tail)...);
}
#ifdef DEBUG_
#define DEB
#define dump(...)                                                              \
    DUMPOUT << "  " << string(#__VA_ARGS__) << ": "                            \
            << "[" << to_string(__LINE__) << ":" << __FUNCTION__ << "]"        \
            << endl                                                            \
            << "    ",                                                         \
        dump_func(__VA_ARGS__)
#else
#define DEB if (false)
#define dump(...)
#endif
Point operator*(const Point &p, const Real &d) {
  return Point(real(p) * d, imag(p) * d);
}
struct Circle {
    Point center; Real radius;
    Circle() {}
    Circle(Point &center, Real &radius): center(center), radius(radius){}
};
inline int sgn(const Real &r) {//r>0:1 r==0:0 r<0:-1
	return (r < -EPS ? -1 : (r > EPS ? +1 : 0));
}
inline Real dot(const Point &a, const Point &b){//内積
    return real(a)*real(b) + imag(a)*imag(b);
}
inline Real det(const Point &a, const Point &b){//外積
    return real(a)*imag(b) - imag(a)*real(b);
}
struct Line {
    Point a, b;
    Line(){};
    Line(Point a,Point b):a(a),b(b){};
};
inline Real dist(const Point &a, const Point &b){
    Vector2d v = b-a;
    return abs(v);
}
inline Real dist(const Circle &a, const Circle &b){//円周と円周を結ぶ最短の距離
    return max(Real(EPS), EPS+dist(a.center, b.center)-a.radius-b.radius);
}
inline Real angle(const Vector2d &a, const Vector2d &b){//ベクトルaから見たベクトルbの角度
    return arg(b) - arg(a);
}
inline bool isParallel(const Vector2d & a, const Vector2d &b){
    return abs(det(a, b)) < EPS;
}
inline bool isOrthogonal(const Vector2d& a,const Vector2d& b){
    return abs(dot(a, b)) < EPS;
}
void sortByArg(vector <Point> & points){//偏角ソート
    sort(points.begin(),points.end(), [](auto const &a, auto const &b) {
        return (sgn(arg(a)-arg(b))==-1);
    });
}

vector <long double> dijkstra(WeightedGraph &G, long double s=0){
    vector <long double> d(G.size(),INF);
    priority_queue<P, vector<P>, greater<P> > que;
    d[s] = 0;
    que.push(P(0,s)); 
    while(!que.empty()){
        P p = que.top(); que.pop();
        long double v = p.second;
        if(d[v]< p.first) continue;
        long double sz = G[v].size();
        rep(i,sz) if(chmin(d[G[v][i].F], d[v] + G[v][i].S)) que.push(P(d[G[v][i].F], G[v][i].F));
    }
    return d;
}

signed main(void) { cin.tie(0); ios::sync_with_stdio(false);
    Point s, e;
    cin>>s>>e;
    int n; cin>>n;
    vector <Circle> circles(n+2);
    circles[0].center = s, circles[0].radius = 0;
    circles[n+1].center = e, circles[n+1].radius = 0;
    rep(i, n){
        Point tmp;
        cin>>tmp;
        long double r; cin>>r;
        circles[i+1].center = tmp, circles[i+1].radius = r;
    }
    
    WeightedGraph g(n+2);
    for(int i=0;i<n+2;i++){
        for(int j=i+1;j<n+2;j++){
            g[i].pb({j, EPS+dist(circles[i], circles[j])});
            g[j].pb({i, EPS+dist(circles[i], circles[j])});
        }
    }
    printf("%.12Lf\n", dijkstra(g)[n+1]);
}


Measured memory_bytes: 42416