#pragma GCC target("avx2")
#pragma GCC optimize("O3")
#pragma GCC optimize("unroll-loops")
#include <bits/stdc++.h>
constexpr long long INF = 1LL << 60;
constexpr long long MOD = 1000000007;
double PI = acos(-1.0);
#define rep(i, n) for (ll i = 0; i < (n); ++i)
#define rep1(i, n) for (ll i = 1; i <= (n); ++i)
#define rrep(i, n) for (ll i = (n - 1); i >= 0; --i)
#define perm(c) sort(ALL(c));for(bool c##p=1;c##p;c##p=next_permutation(ALL(c)))
#define ALL(obj) (obj).begin(), (obj).end()
#define RALL(obj) (obj).rbegin(), (obj).rend()
#define pb push_back
#define to_s to_string
#define len(v) (ll)v.size()
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end())
#define print(x) cout << (x) << '\n'
#define drop(x) cout << (x) << '\n', exit(0)
#define debug(x) cout << #x << ": " << (x) << '\n'
using namespace std;
typedef long long ll;
typedef unsigned long long ull;
typedef pair<ll, ll> P;
typedef tuple<ll, ll, ll> tpl;
typedef vector<ll> vec;
typedef vector<vector<ll>> vec2;
typedef vector<vector<vector<ll>>> vec3;
template<class S, class T> inline bool chmax(S &a, const T &b) { if (a<b) { a=b; return 1; } return 0; }
template<class S, class T> inline bool chmin(S &a, const T &b) { if (b<a) { a=b; return 1; } return 0; }
inline ll msb(ll v) { return 1 << (31 - __builtin_clzll(v)); }
inline ll devc(ll x, ll y) { return (x + y - 1) / y; }
inline ll gcd(ll a, ll b) { return b ? gcd(b, a % b) : a; }
inline ll lcm(ll a, ll b) { return a * (b / gcd(a, b)); }
 
struct IoSetup {
    IoSetup() {
        cin.tie(nullptr);
        ios::sync_with_stdio(false);
        cout << fixed << setprecision(10);
        cerr << fixed << setprecision(10);
    }
} iosetup;
 
template< typename T1, typename T2 >
ostream &operator << (ostream &os, const pair< T1, T2 > &p) {
    os << p.first << " " << p.second;
    return os;
}
 
template< typename T1, typename T2 >
istream &operator >> (istream &is, pair< T1, T2 > &p) {
    is >> p.first >> p.second;
    return is;
}
 
template< typename T1, typename T2, typename T3 >
ostream &operator << (ostream &os, const tuple< T1, T2, T3 > &t) {
    os << get<0>(t) << " " << get<1>(t) << " " << get<2>(t);
    return os;
}
 
template< typename T1, typename T2, typename T3 >
istream &operator >> (istream &is, tuple< T1, T2, T3 > &t) {
    is >> get<0>(t) >> get<1>(t) >> get<2>(t);
    return is;
}
 
template< typename T >
ostream &operator << (ostream &os, const vector< T > &v){
    for (int i = 0; i < (int)v.size(); ++i) {
        os << v[i] << (i + 1 != v.size() ? " " : "");
    }
    return os;
}
 
template< typename T >
istream &operator >>  (istream &is, vector< T > &v){
    for(T &in : v) is >> in;
    return is;
}

template< typename T >
ostream &operator << (ostream &os, const set< T > &st){
    int ct = 0;
    for(auto& s : st) cout << s << (++ct != st.size() ? " " : "");
    return os;
}

template <typename T>
constexpr set<T> &operator|= (set<T> &st1, const set<T> &st2) { 
    for(auto& s : st2) st1.insert(s);
    return st1; 
}

template <typename T>
constexpr set<T> &operator-= (set<T> &st1, const set<T> &st2) {
    for(auto& s : st2) if(st1.count(s)) st1.erase(s);
    return st1;
}

template <typename T>
constexpr set<T> &operator&= (set<T> &st1, const set<T> &st2) {
    auto itr = st1.begin();
    while(itr != st1.end()){
        if(!st2.count(*itr)) itr = st1.erase(itr);
        else ++itr;
    }
    return st1;
}

template <typename T>
constexpr set<T> operator| (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res |= st2;
    return res;
}

template <typename T>
constexpr set<T> operator- (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res -= st2;
    return res;
}

template <typename T>
constexpr set<T> operator& (const set<T> &st1, const set<T> &st2) {
    set<T> res = st1;
    res &= st2;
    return res;
}

/*---------------------------------    Tools    ------------------------------------------*/
template< typename T >
vector<T> cumsum(const vector<T> &X){
    vector<T> res(X.size() + 1, 0);
    for(int i = 0; i < X.size(); ++i) res[i + 1] += res[i] + X[i];
    return res;
}
 
template< typename S, typename T, typename F>
pair<T, T> bisearch(S left, T right, F f) {
    while(abs(right - left) > 1){
        T mid = (right + left) / 2;
        if(f(mid)) right = mid;
        else left = mid;
    }
    return {left, right};
}
 
template< typename S, typename T, typename F>
double trisearch(S left, T right, F f, int maxLoop = 90){
    double low = left, high = right;
    while(maxLoop--){
        double mid_left = high / 3 + low * 2 / 3;
        double mid_right = high * 2 / 3 + low / 3;
        if(f(mid_left) >= f(mid_right)) low = mid_left;
        else high = mid_right;
    }
    return (low + high) * 0.5;
}

template< typename F >
ll ternarySearch(ll L, ll R, F f) { //[L, R)
    ll lo = L - 1, hi = R - 1;
    while (lo + 1 != hi) {
        ll mi = (lo + hi) / 2;
        if (f(mi) <= f(mi + 1)) hi = mi;
        else lo = mi;
    }
    return hi;
}

//Def of Monoid
//Suppose that S is a set and ● is some binary opeartion S x S -> S
//then S with ● is a monoid if it satisfies the following two:
// Associativity(結合則)
//  For all a,b and c in S, the equation (a ● b) ● c = a ● (b ● c) holds
// Identitiy element(単位元の存在)
//  There exisits an element e in S such that for every element a in S,
//  the equations e ● a = a ● e = a holds

//Eample of Monoid
//+, *, and, or, xor, min, max

//Build O(N)
//Query O(log N)
//- query(a,b) : applay operation to the range [a, b)
//- update(k,x) : change k-th element to x
//- operator[k] : return k-th element

template< typename Monoid >
class SegmentTree{
    private:
        using F = function<Monoid(Monoid, Monoid)>;
        
        long long sz;
        vector<Monoid> seg;
        const F f;
        const Monoid e;

    public:
        SegmentTree(long long n, const F f, const Monoid &e) : f(f), e(e){
            sz = 1;
            while(sz < n) sz <<= 1;
            seg.assign(2 * sz, e);
        }

        void set(long long k, const Monoid &x){
            seg[k + sz] = x;
        }

        void build() {
            for (long long k = sz - 1; k > 0; --k){
                seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
            }
        }

        void update(long long k, const Monoid &x) {
            k += sz;
            seg[k] = x;
            while(k >>= 1) seg[k] = f(seg[2 * k + 0], seg[2 * k + 1]);
        }

        Monoid query(long long a, long long b){
            Monoid L = e, R = e;
            for (a += sz, b += sz; a < b; a >>= 1, b >>= 1){
                if(a & 1) L = f(L, seg[a++]);
                if(b & 1) R = f(seg[--b],R);
            }
            return f(L, R);
        }

        Monoid operator[](const int &k) const {
            return seg[k + sz];
        }
};

/*---------------------------------    Graph    ------------------------------------------*/
struct Graph {
    struct Edge {
        ll from, to;
        double weight;
        Edge() : from(0), to(0), weight(0) {}
        Edge(ll f, ll t, double w) : from(f), to(t), weight(w) {}
    };
    using Edges = vector<Edge>;

    vector<Edges> G;

    Graph() : G() {};

    Graph(int N) : G(N) {}

    Edges operator[](int k) const{
        return G[k];
    }

    ll size() const{
        return G.size();
    }

    void resize(int N){
        G.resize(N);
    }

    void add_edge(int a, int b, double w = 1){
        G[a].emplace_back(a, b, w);
        G[b].emplace_back(b, a, w);
    }

    void add_arrow(int a, int b, double w = 1){
        G[a].emplace_back(a, b, w);
    }

    //Topological_sort
    //!!return empty, if not DAG
    vector<ll> topological_sort() const;

    //Dijkstra and related
    vector<double> dijkstra(ll s, bool restore = false) const;

    vector<ll> shortest_path(ll start, ll goal) const;

    //Bellman-Ford
    //!!return empty, if negative loop exists
    vector<ll> bellman_ford(ll s) const;

    //Warshall-Floyd
    vector<vector<ll>> Warshall_Floyd() const; 

    //Kruskal
    //!!Required UnionFind
    Graph Kruskal() const;
};


vector<double> Graph::dijkstra(ll s, bool restore) const{
    vector<double> dist(G.size(), INF);
    priority_queue<pair<double, ll>, vector<pair<double, ll>>, greater<pair<double, ll>>> que;
    dist[s] = 0;
    que.emplace(dist[s], s);

    vector<double> prev(G.size(), -1);

    while(!que.empty()){
        double cost;
        int idx;
        tie(cost, idx) = que.top();
        que.pop();
        if(dist[idx] < cost) continue;
        for(auto &e : G[idx]){
            auto next_cost = cost + e.weight;
            if(dist[e.to] <= next_cost) continue;
            dist[e.to] = next_cost;

            if(restore) prev[e.to] = e.from;
            que.emplace(dist[e.to], e.to);
        }
    }
    if(restore) return prev;
    return dist;
}

/*---------------------------------   Geometry   -----------------------------------------*/
using Point = complex<double>;
const double EPS = 1e-12;

struct Line : vector<Point> {
    Line(Point a = Point(0.0, 0.0), Point b = Point(0.0, 0.0)){
        this->push_back(a);
        this->push_back(b);
    }
    friend ostream &operator<<(ostream &s, const Line &l) { return s << '{' << l[0] << ',' << l[1] << '}'; }
};

/* ∠ABC */
double degree(Point A, Point B, Point C){
    if(B == C) return 0;
    return arg((A - B) / (C - B));
}

/* counter-clockwise */
/* AB, ACの関係性を調べる*/
/* 同一直線上 : positive, 非同一直線上 : negative*/
/* 同一直線上だが、CはAB上に無い : 3 */
/* 同一直線上でCはAB上の点 : 2 */
/* 同一直線上で逆向きにCが存在 : 1 */
/* AB -> ACが反時計周り : -1 */
/* AB -> ACが時計周り : -2 */
//VERIFIED : http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_1_C
int ccw(Point A, Point B, Point C){
    double deg = degree(B, A, C);
    if(abs(cos(deg) - 1.0) <= EPS){
        if(abs(C - A) > abs(B - A)) return 3;
        else  return 2;
    }
    if(abs(cos(deg) + 1) <= EPS) return 1;

    if(sin(deg) + EPS >= 0) return -2;
    else return -1;
}
 
/* perpendicular bisector */
Line bisector(const Line& L){
    Point X = L[0], Y = L[1];
    Point C = (X + Y) / 2.0;
    Point D = C + (X - Y) * Point(0.0, 1.0);
    return Line(C, D);
}

/* 二直線間の角度, 平行, 垂直 */
//VERIFIED : http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_A
double lineAngle(const Line& L1, const Line& L2){
    return degree(Point(L1[1] - L1[0] ), Point(0.0, 0.0), Point(L2[1] - L2[0]));
}

bool isParallel(const Line& L1, const Line& L2){
    return abs(sin(lineAngle(L1, L2))) <= EPS;
}

bool isOrthogonal(const Line& L1, const Line& L2){
    return abs(cos(lineAngle(L1, L2))) <= EPS;
}

/* cross point */
/* 二直線の交点 */
// VERIFIED : http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_C
Point crosspoint(const Line& L1, const Line& L2){
    if(isParallel(L1, L2)) return Point(-INF, -INF);
    Point A = L1[0], B = L1[1];
    Point C = L2[0], D = L2[1];
    return A + (B - A) * (imag((A - C) * conj(C - D)) / imag((C - D) * conj(B - A)));
}

/* Line Segment Crossed? */
/* 線分の交差判定 */
// VERIFIED : http://judge.u-aizu.ac.jp/onlinejudge/description.jsp?id=CGL_2_B
bool isSegmentCrossed(const Line& L1, const Line& L2){
    Point A = L1[0], B = L1[1];
    Point C = L2[0], D = L2[1];

    if(isParallel(L1, L2)){
        if(ccw(A, B, C) == 2 or ccw(A, B, D) == 2 or ccw(C, D, A) == 2 or ccw(C, D , B) == 2) return true;
        return false;
    }


    double t = imag((A - C) * conj(C - D)) / imag((C - D) * conj(B  - A));
    double s = imag((C - A) * conj(A - B)) / imag((A - B) * conj(D - C));
    return t + EPS >= 0 and t - EPS <= 1 and s + EPS >= 0 and s - EPS <= 1;
}

/* foot of a perpendicular line　*/
/* 垂線の足 */
//TODO : バグってる
Point foot(const Point &A, const Line &L){
    return (A + L[0] + L[1] - (A * L[0] * conj(L[1]))) / 2.0;
};

/*------------------------------- Main Code Here -----------------------------------------*/
 
int main()
{
    ll xs, ys, xt, yt;
    cin >> xs >> ys >> xt >> yt;

    ll N;
    cin >> N;
    vector<tpl> B(N + 2);
    B[0] = {xs, ys, 0};
    B[N + 1] = {xt, yt, 0};
    for(ll i = 1; i <= N; ++i) cin >> B[i];

    Graph G(N + 2); 
    rep(i, N + 2) rep(j, N + 2) if(i < j){
        auto [xa, ya, ra] = B[i];
        auto [xb, yb, rb] = B[j];

        Point A(xa, ya), B(xb, yb);

        double d = abs(A - B) - ra - rb;
        chmax(d, 0);
        G.add_edge(i, j, d);
    }

    auto res = G.dijkstra(0);

    print(res[N + 1]);







    
 

    return 0;
}     

Measured memory_bytes: 31884