//#define _GLIBCXX_DEBUG
#include <bits/stdc++.h>
#define rep(i, n) for(int i=0; i<n; ++i)
#define all(v) v.begin(), v.end()
#define rall(v) v.rbegin(), v.rend()
using namespace std;
using ll = int64_t;
using ld = long double;
using P = pair<int, int>;
using vs = vector<string>;
using vi = vector<int>;
using vvi = vector<vi>;
template<class T> using PQ = priority_queue<T>;
template<class T> using PQG = priority_queue<T, vector<T>, greater<T> >;
const int INF = 100010001;
const ll LINF = (ll)INF*INF*10;
template<typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) {return a < b && (a = b, true);}
template<typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) {return a > b && (a = b, true);}
template<typename T1, typename T2>
istream &operator>>(istream &is, pair<T1, T2> &p) { return is >> p.first >> p.second;}
template<typename T1, typename T2>
ostream &operator<<(ostream &os, const pair<T1, T2> &p) { return os << p.first << ' ' << p.second;}

struct edge {
    int to;
    double cost;
    edge(int x=0, double y=0):to(x), cost(y) {}
};

vector<vector<edge> > G; // resizeの必要あり

struct dijkstra {
    vector<double> d;
    dijkstra(int s, int n):d(n, INT64_MAX/3) { // sはスタート,nは頂点数
        d[s] = 0LL;
        priority_queue<pair<double, int>, vector<pair<double, int> >, greater<pair<double, int> > > que;
        que.push(make_pair(0LL, s));
        while(!que.empty()) {
            pair<double, int> now = que.top();
            que.pop();
            if(now.first != d[now.second]) continue;
            for(edge next:G[now.second]) {
                if(d[next.to] > d[now.second] + next.cost) {
                    d[next.to] = d[now.second] + next.cost;
                    que.push(make_pair(d[next.to], next.to));
                }
            }
        }
    }
};

const double EPS = 1e-10;
double add(double a, double b) {
    if(abs(a+b) < EPS*(abs(a)+abs(b))) return 0;
    return a+b;
}
struct Vector {
    double x, y;
    Vector(double x=0, double y=0):x(x), y(y) {}
    Vector operator+(Vector v) {return Vector(add(x, v.x), add(y, v.y));}
    Vector operator-(Vector v) {return Vector(add(x, -v.x), add(y, -v.y));}
    Vector operator*(double d) {return Vector(x*d, y*d);}
    Vector operator/(double d) {return Vector(x/d, y/d);}
    double dot(Vector v) {return add(x*v.x, y*v.y);}
    double cross(Vector v) {return add(x*v.y, -y*v.x);}
    Vector rotate(double theta) {return Vector(add(x*cos(theta), -y*sin(theta)), add(x*sin(theta), y*cos(theta)));}
};
const Vector origin = Vector(0, 0);
struct Circle {
    Vector c;
    double r;
    Circle(Vector c=Vector(), double r=0):c(c), r(r) {}
};
istream &operator>>(istream &is, Vector &v) {return is >> v.x >> v.y;}
ostream &operator<<(ostream &os, const Vector &v) {return os << v.x << ' ' << v.y;}
istream &operator>>(istream &is, Circle &c) {return is >> c.c >> c.r;}
ostream &operator<<(ostream &os, const Circle &c) {return os << c.c << ' ' << c.r;}
double sqdist(Vector v, Vector u) {return (v-u).dot(v-u);}
//線分v2-v1上にあるか
bool on_seg(Vector &v1,Vector &v2, const Vector &p) {
    return (v1-p).cross(v2-p) == 0 && (v1-p).dot(v2-p) <= 0;
}
//v1-v2とu1-u2の交点
Vector intersection(Vector &v1,Vector &v2,Vector &u1,Vector &u2) {
    assert((v1-v2).cross(u1-u2)); //2直線が平行だとだめ
    return v1 + (v2-v1)*((u2-u1).cross(u1-v1)/(u2-u1).cross(v2-v1));
}
//p2-p1へのQの投影
Vector projection(Vector &p1,Vector &p2,Vector &Q) {
    return p1+(p2-p1)*(Q-p1).dot(p2-p1)/sqdist(p1, p2);
}
//p1-p2を軸としたQの線対称移動
Vector reflection(Vector &p1,Vector &p2,Vector &Q) {
    return projection(p1, p2, Q)*2-Q;
}
//2円が2点で交わりを持つか
bool com_cir(Circle &a, Circle &b) {
    return add((a.r+b.r)*(a.r+b.r), - sqdist(a.c, b.c)) > 0;
}
//円aが円bを真に含んでいるか
bool over_cir(Circle &a, Circle &b) {
    return add(a.r - sqrt(sqdist(a.c, b.c)), -b.r) > 0;
}
//円aが円bを含む&接している
bool intouch_cir(Circle &a, Circle &b) {
    return add(a.r - sqrt(sqdist(a.c, b.c)), -b.r) == 0;
}
//円aが円bを含まない&接している
bool outtouch_cir(Circle &a, Circle &b) {
    return add((a.r+b.r)*(a.r+b.r), - sqdist(a.c, b.c)) == 0;
}
//円aが真に含むか
bool in_cir(Circle &a, Vector &p) {
    return add(sqdist(a.c, p), -a.r*a.r) < 0;
}
//円周上にあるか
bool on_cir(Circle &a, Vector &p) {
    return add(sqdist(a.c, p), -a.r*a.r) == 0;
}
bool cmp_x(const Vector &v, const Vector &u) {
    if(v.x != u.x) return v.x < u.x;
    return v.y < u.y;
}
bool cmp_y(const Vector &v, const Vector &u) {
    if(v.y != u.y) return v.y < u.y;
    return v.x < u.x;
}
//凸包 頂点数nの頂点集合vv
vector<Vector> convex_hull(vector<Vector> &vv, int n) {
    sort(vv.begin(), vv.end(), cmp_x);
    int k = 0;
    vector<Vector> res(n*2);
    for(int i = 0; i < n; i++) {
        while(k > 1 && (res[k-1]-res[k-2]).cross(vv[i]-res[k-1]) <= 0) k--;
        res[k++] = vv[i];
    }
    for(int i = n-2, t = k; i >= 0; i--) {
        while(k > t && (res[k-1]-res[k-2]).cross(vv[i]-res[k-1]) <= 0) k--;
        res[k++] = vv[i];
    }
    res.resize(k-1);
    return res;
}
//点と線の距離
double distpl(Vector &p0, Vector &p1, Vector &Q) {
    Vector pp = projection(p0, p1, Q);
    return sqrt(sqdist(pp, Q));
}
//線分と線分の距離
double distss(Vector &p0, Vector &p1, Vector &p2, Vector &p3) {
    if((p0-p1).cross(p2-p3) != 0) {
        Vector p = intersection(p0, p1, p2, p3);
        if(on_seg(p0, p1, p) and on_seg(p2, p3, p)) {
            return 0.0;
        }
    }
    double res = min({sqdist(p0, p2), sqdist(p0, p3), sqdist(p1, p2), sqdist(p1, p3)});
    Vector pp0, pp1, pp2, pp3;
    pp2 = projection(p0, p1, p2);
    pp3 = projection(p0, p1, p3);
    pp0 = projection(p2, p3, p0);
    pp1 = projection(p2, p3, p1);
    if(on_seg(p0, p1, pp2)) res = min(res, sqdist(pp2, p2));
    if(on_seg(p0, p1, pp3)) res = min(res, sqdist(pp3, p3));
    if(on_seg(p2, p3, pp0)) res = min(res, sqdist(pp0, p0));
    if(on_seg(p2, p3, pp1)) res = min(res, sqdist(pp1, p1));
    res = sqrt(res);
    return res;
}

int main() {
    cout << fixed << setprecision(13);
    ios::sync_with_stdio(false);
    cin.tie(0);
    Vector s, t;
    cin >> s >> t;
    int n;
    cin >> n;
    vector<Circle> c(n);
    G.resize(n+2);
    rep(i, n) {
        cin >> c[i];
        rep(j, i) {
            G[j].emplace_back(i, max(0.0, sqrt(sqdist(c[i].c, c[j].c)) - c[i].r - c[j].r));
            G[i].emplace_back(j, max(0.0, sqrt(sqdist(c[i].c, c[j].c)) - c[i].r - c[j].r));
        }
    }

    rep(i, n) {
        G[n].emplace_back(i, max(0.0, sqrt(sqdist(s, c[i].c)) - c[i].r));
        G[i].emplace_back(n+1, max(0.0, sqrt(sqdist(t, c[i].c)) - c[i].r));
    }

    cout << min(dijkstra(n, n+2).d[n+1], sqrt(sqdist(s, t))) << endl;
}


Measured memory_bytes: 23580