#include <limits>
#include <initializer_list>
#include <utility>
#include <bitset>
#include <tuple>
#include <type_traits>
#include <functional>
#include <string>
#include <array>
#include <deque>
#include <list>
#include <queue>
#include <stack>
#include <vector>
#include <map>
#include <set>
#include <unordered_map>
#include <unordered_set>
#include <iterator>
#include <algorithm>
#include <complex>
#include <random>
#include <numeric>
#include <iostream>
#include <iomanip>
#include <sstream>
#include <regex>
#include <cassert>
#include <cstddef>
// #include <variant>

// Yay!!
#define endl codeforces

// macros for iterator
#define ALL(v) std::begin(v), std::end(v)
#define ALLR(v) std::rbegin(v), std::rend(v)

// alias
using ll = std::int64_t;
using ull = std::uint64_t;
using pii = std::pair<int, int>;
using tii = std::tuple<int, int, int>;
using pll = std::pair<ll, ll>;
using tll = std::tuple<ll, ll, ll>;
template <typename T> using vec = std::vector<T>;
template <typename T> using vvec = vec<vec<T>>;

// variadic min/max
template <typename T> const T& var_min(const T &t) { return t; }
template <typename T> const T& var_max(const T &t) { return t; }
template <typename T, typename... Tail> const T& var_min(const T &t, const Tail&... tail) { return std::min(t, var_min(tail...)); }
template <typename T, typename... Tail> const T& var_max(const T &t, const Tail&... tail) { return std::max(t, var_max(tail...)); }

// variadic chmin/chmax
template <typename T, typename... Tail> void chmin(T &t, const Tail&... tail) { t = var_min(t, tail...); }
template <typename T, typename... Tail> void chmax(T &t, const Tail&... tail) { t = var_max(t, tail...); }

// multi demension array
template <typename T, std::size_t Head, std::size_t... Tail> struct multi_dim_array { using type = std::array<typename multi_dim_array<T, Tail...>::type, Head>; };
template <typename T, std::size_t Head> struct multi_dim_array<T, Head> { using type = std::array<T, Head>; };
template <typename T, std::size_t... Args> using mdarray = typename multi_dim_array<T, Args...>::type;

// fill container
// template <typename T, typename F, typename... Args> 
// void fill_seq(T &t, F f, Args... args) { if constexpr (std::is_invocable<F, Args...>::value) { t = f(args...); } else { for (ssize_t i = 0; i < t.size(); i++) fill_seq(t[i], f, args..., i); } }

// make multi dimension vector
template <typename T> vec<T> make_v(ssize_t sz) { return vec<T>(sz); }
template <typename T, typename... Tail> auto make_v(ssize_t hs, Tail&&... ts) { auto v = std::move(make_v<T>(std::forward<Tail>(ts)...)); return vec<decltype(v)>(hs, v); }

// init
namespace init__ { 
struct InitIO { InitIO() { std::cin.tie(nullptr); std::ios_base::sync_with_stdio(false); std::cout << std::fixed << std::setprecision(30); } } init_io; 
}


int main() {
    ll a0, b0, a1, b1;
    std::cin >> a0 >> b0 >> a1 >> b1;
    vec<tll> cv;
    cv.emplace_back(a0, b0, 0);
    ll n;
    std::cin >> n;
    for (ll i = 0; i < n; i++) {
        ll a, b, r;
        std::cin >> a >> b >> r;
        cv.emplace_back(a, b, r);
    }
    cv.emplace_back(a1, b1, 0);

    auto pow2 = [](ll x) { return x * x; };

    vvec<std::pair<ll, double>> g(n + 2);
    for (ll i = 0; i < n + 2; i++) for (ll j = i + 1; j < n + 2; j++) {
        auto a = cv[i], b = cv[j];
        ll x0, y0, r0, x1, y1, r1;
        std::tie(x0, y0, r0) = a;
        std::tie(x1, y1, r1) = b;
        ll dx = x0 - x1;
        ll dy = y0 - y1;
        ll d2 = pow2(dx) + pow2(dy);
        double cost = 0;
        if (pow2(r0 + r1) < d2) cost = std::sqrt(d2) - (r0 + r1);
        g[i].emplace_back(j, cost);
        g[j].emplace_back(i, cost);
    }

    using node = std::pair<double, ll>;
    std::priority_queue<node, vec<node>, std::greater<node>> pq;
    const double inf = 5e15;
    pq.emplace(0, 0);
    vec<double> dists(n + 2, inf);
    dists[0] = 0;
    while (pq.size()) {
        double d;
        ll cur;
        std::tie(d, cur) = pq.top();
        pq.pop();
        if (dists[cur] < d) continue;
        for (auto &&e : g[cur]) {
            double cost;
            ll nxt;
            std::tie(nxt, cost) = e;
            double nd = cost + d;
            if (dists[nxt] <= nd) continue;
            dists[nxt] = nd;
            pq.emplace(nd, nxt);
        }
    }

    std::cout << dists.back() << "\n";
    return 0;
}


Measured memory_bytes: 22768