#include <bits/stdc++.h>
using namespace std;
#define rep(i,n) for (int i = 0; i < int(n); i++)
#define rep1(i,n) for (int i = 1; i <= int(n); i++)
#define repR(i,n) for (int i = int(n)-1; i >= 0; i--)
#define rep1R(i,n) for (int i = int(n); i >= 1; i--)
#define all(x) (x).begin(), (x).end()
#define pb push_back
#define eb emplace_back
#define mp make_pair
#define fst first
#define snd second
#define cauto const auto
#ifdef LOCAL
#define dump(...) cerr << "[" << __LINE__ << ":" << __FUNCTION__ << "] ", _dmp_(#__VA_ARGS__, __VA_ARGS__);
void _dmp_(const char*) { cerr << endl; }
template <class T, class... U>
void _dmp_(const char *s, T const& x, U const& ...y) { const char *o = "({[", *e = "]})"; for (int i = 0; *s != '\0'; cerr << *s++) { if (count(o,o+3,*s)) i++; if (count(e,e+3,*s)) i--; if (!i && *s == ',') break; } cerr << " = " << x; if (*s == ',') cerr << ", ", s++; _dmp_(s, y...); }
#else
#define dump(...)
#endif
using ll = long long;
#define int ll
template <class T> using pque_max = priority_queue<T>;
template <class T> using pque_min = priority_queue<T, vector<T>, greater<T> >;
#define CONAINER_OUTPUT os << "{"; for (auto const& x : v) os << " " << x; return os << " }";
template <class T> ostream& operator<<(ostream& os, vector<T> const& v) { CONAINER_OUTPUT }
template <class T> ostream& operator<<(ostream& os, deque<T> const& v) { CONAINER_OUTPUT }
template <class T> ostream& operator<<(ostream& os, set<T> const& v) { CONAINER_OUTPUT }
template <class T, class U> ostream& operator<<(ostream& os, map<T,U> const& v) { CONAINER_OUTPUT }
#undef CONAINER_OUTPUT
template <class T> istream& operator>>(istream& is, vector<T>& v) { for (auto& x : v) is >> x; return is; }
template <class T, class S> ostream& operator<<(ostream& os, pair<T,S> const& p) { return os << "(" << p.first << ", " << p.second << ")"; }
template <class T, class S> istream& operator>>(istream& is, pair<T,S> const& p) { return is >> p.first >> p.second; }
struct _Init_ { _Init_() { cin.tie(nullptr); ios::sync_with_stdio(false); cout << fixed << setprecision(20); } } _init_;

template <class T> void quit(T const& x) { cout << x << endl; exit(0); }
template <class T> bool chmin(T& x, T const& y) { if (x > y) { x = y; return true; } return false; }
template <class T> bool chmax(T& x, T const& y) { if (x < y) { x = y; return true; } return false; }
#define YesNo(c) ((c) ? "Yes" : "No")
////////////////////////////////

using Cost = double;
vector<Cost> dijkstra(vector<vector<pair<Cost,int> > > const& g, int s) {
    int n = g.size();
    vector<Cost> d(n);
    rep (i,n) d[i] = -1;
    pque_min<pair<Cost,int> > q;
    q.emplace(0,s);
    while (!q.empty()) {
        auto p = q.top(); q.pop();
        if (d[p.snd] != -1) continue;
        d[p.snd] = p.fst;
        for (cauto& x : g[p.snd]) q.emplace(d[p.snd] + x.fst, x.snd);
    }
    return d;
}

int sq(int x) { return x*x; }

int32_t main() {
    int xs,ys,xt,yt; cin >> xs >> ys >> xt >> yt;
    int n; cin >> n;
    vector<int> x(n+2), y(n+2), r(n+2);
    rep (i,n) cin >> x[i] >> y[i] >> r[i];
    const int s = n, t = n+1;
    x[s] = xs, y[s] = ys, x[t] = xt, y[t] = yt, r[s] = r[t] = 0;

    vector<vector<pair<double, int> > > g(n+2);
    rep (i,n+2) rep (j,n+2) if (i < j) {
        double d = sq(x[i]-x[j]) + sq(y[i]-y[j]);
        d = max(0.0, sqrt(d) - (r[i] + r[j]));
        g[i].emplace_back(d,j);
        g[j].emplace_back(d,i);
    }
    auto v = dijkstra(g,s);
    cout << v[t] << endl;

    //
    dump(g);
    dump(v);
}


Measured memory_bytes: 35084