/**
 * code generated by JHelper
 * More info: https://github.com/AlexeyDmitriev/JHelper
 * @author Gosu_Hiroo
 */

#include <iostream>
#include <fstream>

#include <bits/stdc++.h>
using namespace std;

typedef long long ll;
#define tr(container, it) \
        for (auto it = container.begin(); it != container.end(); it++)
#define scontains(c, x) ((c).find(x) != (c).end())   //O(log n)
#define contains(c, x) (find((c).begin(),(c).end(),x) != (c).end()) //O(n)
#define pll pair<ll,ll>
#define pii pair<int,int>
#define mll map<ll,ll>
#define intv(x, a, b)((x)>=a && (x)<=b)
#define  rep(i, _begin, _end) for (__typeof(_end) end = _end, begin = _begin,  i = (begin) - ((begin) > (end)); i != (end) - ((begin) > (end)); i += 1 - 2 * ((begin) > (end)))
#define  _for(i, end) for (__typeof(end) i = 0, _len = (end); i < (_len); i += 1)
#define all(x) (x).begin(),(x).end()
#define SZ(x) ((int)(x).size())
#define F first
#define S second
#define y0 y3487465
#define y1 y8687969
#define j0 j1347829
#define j1 j234892
#define what_is(x) cerr << #x << " is " << x << endl;
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args,cerr); }
#define mod(x, m) ((((x) % (m)) + (m)) % (m))
#define bit(n) (1LL<<(n))
#define UNIQUE(v) v.erase( unique(v.begin(), v.end()), v.end() );
#define readint ({int t;cin >> t;t;})
#define fcout cout << fixed << setprecision(12)
#define fcerr cerr << fixed << setprecision(12)
const double PI = 2 * acos(.0);
const int INF = 0x3f3f3f3f;
const ll LLINF = 1000000000000000005LL;;
const ll MOD = (ll) (1e9) + 7;
void _mod(ll &x){x = mod(x, MOD);}
//const ll MOD = (ll) 998244353 ;
const double EPS = 1e-10;
int dx[4]={1,0,-1,0};
int dy[4]={0,1,0,-1};

void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args, std::ostream& cerr) {
    cerr << *it << " = " << a << endl;
    err(++it, args...);
}

template<typename A, size_t N, typename T>
void Fill(A (&array)[N], const T &val) {
    std::fill((T *) array, (T *) (array + N), val);
}

template <typename T>
ostream& operator << (ostream& os, const vector<T> V) {
    for(auto v : V)os << v << ", ";
    return os;
}



template <typename T>
ostream& operator << (ostream& os, const set<T> V) {
    for(auto v : V)os << v << ", ";
    return os;
}

template <typename T>
ostream& operator << (ostream& os, const deque<T> V) {
    for(auto v : V)os << v << ", ";
    return os;
}

template<class T>bool chmax(T &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class T>bool chmin(T &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }

//#define int ll

//const int maxV=114514;

class ECosmicRays {
public:
    struct Barrier{
        double x,y,r;
    }Barriers[1011];


    template<typename T>
    struct wGraph{
        struct edge{
            int to;T cost;
            bool operator > (const edge R)const{
                return cost > R.cost;
            }
        };

     vector<vector<edge>> adj;
     vector<T> dist;
     int V;
     wGraph(int V): V(V), adj(V),dist(V){};

     void addEdge(int u, int v, T weight){
//         adj[u].emplace_back(v, weight);
            adj[u].push_back((edge){v, weight});
     }

        double dijkstra(int s){
            priority_queue<edge,vector<edge>,greater<edge> > que;
            for(int i=0;i<V;i++){dist[i] = 1e300;}
            dist[s]=0;
            que.push({s,0});
            while(!que.empty()){
                edge p = que.top();
                que.pop();
                int v = p.to;
                if(dist[v]<p.cost)continue;
                for(edge e : adj[v]){
                    if(dist[e.to] > dist[v] + e.cost){
                        dist[e.to] = dist[v] + e.cost;
                        que.push({e.to, dist[e.to]});
                    }
                }
            }
        };
    };
void solve(std::istream& cin, std::ostream& cout, std::ostream& cerr) {
    double xs,ys,xt,yt;
    cin >> xs >> ys >> xt >> yt;
    int N;
    cin >> N;
    Barriers[0] = {xs,ys,0};
    rep(i,1,N+1){
        cin >> Barriers[i].x >> Barriers[i].y >> Barriers[i].r;
    }
    Barriers[N+1]= {xt,yt,0};
    wGraph<double> G(N+2);
    _for(i,N+2)_for(j,N+2){
        double w = max(0., sqrt((Barriers[i].x - Barriers[j].x)*(Barriers[i].x - Barriers[j].x) +
                                  (Barriers[i].y - Barriers[j].y)*(Barriers[i].y - Barriers[j].y)) - Barriers[i].r - Barriers[j].r);
        G.addEdge(i, j, w);
//        G.addEdge(j, i, w);
    }

    G.dijkstra(0);
//    _for(i,N+2)error(G.adj[i])
    error(G.dist)
    fcout << G.dist[N+1] << endl;





}


};


#undef int
int main() {

	ECosmicRays solver;
	std::istream& in(std::cin);
	std::ostream& out(std::cout);
    std::ostringstream err;
	in.tie(0); ios::sync_with_stdio(0);
//	solver.solve(in, out);
    solver.solve(in, out,err);
	return 0;
}


Measured memory_bytes: 22128