#include <bits/stdc++.h>
#define endl '\n'
#define int long long
#define lint long long
#define pii pair<int, int>
#define FOR(i, a, b) for(int i = (a); i < (b); ++i)
#define FORR(i, a, b) for(int i = (a); i > (b); --i)
#define REP(i, n) FOR(i, 0, n)
#define SZ(v) ((int)v.size())
#define ZERO(a) memset(a, 0, sizeof(a))
#define MINUS(a) memset(a, 0xff, sizeof(a))
#define FILLINF(a) memset(a, 0x3f, sizeof(a))
#define POW(n) (1LL << (n))
#define POPCNT(n) (__builtin_popcount(n))
#define IN(i, a, b) ((a) <= (i) && (i) <= (b))
using namespace std;
template <typename T> inline bool CHMIN(T& a, T b) { if(a > b) { a = b; return 1; } return 0; }
template <typename T> inline bool CHMAX(T& a, T b) { if(a < b) { a = b; return 1; } return 0; }
template <typename T> inline void SORT(T& a) { sort(begin(a), end(a)); }
template <typename T> inline void REV(T& a) { reverse(begin(a), end(a)); }
template <typename T> inline void UNI(T& a) { sort(a.begin(), a.end()); a.erase(unique(a.begin(), a.end()), a.end()); }
template <typename S, typename T> inline T LB(S& v, T a) { return *lower_bound(begin(v), end(v), a); }
template <typename S, typename T> inline int LBP(S& v, T a) { return lower_bound(begin(v), end(v), a) - begin(v); }
template <typename S, typename T> inline T UB(S& v, T a) { return *upper_bound(begin(v), end(v), a); }
template <typename S, typename T> inline int UBP(S& v, T a) { return upper_bound(begin(v), end(v), a) - begin(v); }
template <typename S, typename T> ostream& operator << (ostream& os, const pair<S, T>& p) { os << p.first << " " << p.second; return os; }
template <typename S, typename T> istream& operator >> (istream& is, pair<S, T>& p) { is >> p.first >> p.second; return is; }
template <typename T> ostream& operator << (ostream& os, const vector<T>& v) { for (int i = 0; i < v.size(); ++i) { if (i) os << " "; os << v[i]; } return os; }
template <typename T> istream& operator >> (istream& is, vector<T>& v) { for(T& in : v) is >> in; return is; }
template <typename T = int> vector<T> make_v(size_t a) { return vector<T>(a); }
template <typename T, typename... Ts> auto make_v(size_t a, Ts... ts) { return vector<decltype(make_v<T>(ts...))>(a,make_v<T>(ts...)); }
template <typename T, typename V> typename enable_if<is_class<T>::value == 0>::type fill_v(T& t, const V& v) { t = v; }
template <typename T, typename V> typename enable_if<is_class<T>::value != 0>::type fill_v(T& t, const V& v) { for(auto &e : t) fill_v(e, v); }
const double PI = 3.14159265358979323846;
const double EPS = 1e-10;
const lint INF = 0x3f3f3f3f3f3f3f3f;
const lint MOD = 1000000007;

struct edge {
    int to;
    double cost;
    edge() = default;
    edge(int to, double cost) : to(to), cost(cost) {}
};

int sx, sy, tx, ty;
int N;
int x[1010], y[1010], r[1010];
vector<edge> g[1010];
double dis[1010];

double dist(int x1, int y1, int r1, int x2, int y2, int r2) {
    double d = hypot(x1 - x2, y1 - y2);
    return max(0.0, d - r1 - r2);
}

void _main() {
    cin >> sx >> sy >> tx >> ty >> N;
    REP (i, N) cin >> x[i] >> y[i] >> r[i];
    x[N] = sx, y[N] = sy;
    x[N + 1] = tx, y[N + 1] = ty;
    REP (i, N + 2) FOR (j, i + 1, N + 2) {
        double d = dist(x[i], y[i], r[i], x[j], y[j], r[j]);
        g[i].emplace_back(j, d);
        g[j].emplace_back(i, d);
    }
    REP (i, N + 2) dis[i] = 1e12;
    dis[N] = 0;
    using P = pair<double, int>;
    priority_queue<P, vector<P>, greater<P>> que;
    que.emplace(0, N);
    while (!que.empty()) {
        P p = que.top(); que.pop();
        if (p.first > dis[p.second]) continue;
        for (edge e : g[p.second]) {
            if (dis[e.to] > p.first + e.cost) {
                dis[e.to] = p.first + e.cost;
                que.emplace(dis[e.to], e.to);
            }
        }
    }
    cout << dis[N + 1] << endl;
}

signed main() {
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cout << fixed << setprecision(10);
    _main();
    return 0;
}

Measured memory_bytes: 22128