#ifndef DEBUG
#  define NDEBUG
#endif
#include <iostream>
#include <algorithm>
#include <string>
#include <iterator>
#include <utility>
#include <type_traits>
#include <limits>
#include <cassert>
#include <numeric>
#include <vector>
#include <queue>
#include <cmath>
#include <tuple>

using namespace std;

// template {{{
// misc {{{
using Z = long long;
[[maybe_unused]]
constexpr Z INF = numeric_limits<Z>::max() / 3;
// }}}

// debug {{{
template <class T>
using enable_if_sequence_t = enable_if_t<
  is_same<
    typename iterator_traits<
      typename remove_cv_t<remove_reference_t<T>>::iterator
    >::iterator_category,
    random_access_iterator_tag>{}>;
#ifdef NDEBUG
# define dump(x)
# define debug if (0)
template <class T>
inline T&& ix(T&& value) { return value; }
template <class T, class Index, class... Indices, class = enable_if_sequence_t<T>>
inline auto&& ix(T&& container, Index index, Indices... indices) {
  return ix(container[index], indices...);
}
#else
# define dump(x) do { \
    cerr << "\e[33m[dump: " << __LINE__ << "] " << (#x) << " = " << x << "\e[0m" << endl; \
  } while (0);
# define debug
template <class T>
inline auto&& ix_impl([[maybe_unused]] int line, [[maybe_unused]] const char* code, T&& value) {
  return value;
}
template <class T, class Index, class... Indices, class = enable_if_sequence_t<T>>
inline auto&& ix_impl(int line, const char* code, T&& container, Index index, Indices... indices) {
  if (index < 0) {
    cerr << "\e[31mix: negative index at line " << line << ", ix(" << code << ")\e[0m" << endl;
    exit(1);
  }
  int size = container.size();
  if (index >= size) {
    cerr << "\e[31mix: index out of range at line " << line << ", ix(" << code << ")\n"
      << "index = " << index << " whereas size = " << size << "\e[0m" << endl;
    exit(1);
  }
  return ix_impl(line, code, container[index], indices...);
}
#define ix(...) ix_impl(__LINE__, #__VA_ARGS__, __VA_ARGS__)
#endif
// }}}

// IO {{{
template <class T, class U>
ostream& operator<< (ostream& os, pair<T, U> p) {
  os << '(' << p.first << ", " << p.second << ')';
  return os;
}
template <class T, class U>
istream& operator>> (istream& is, pair<T, U>& p) {
  is >> p.first >> p.second;
  return is;
}
template <class T>
false_type is_container_impl(...);
template <class T, class = typename T::iterator>
true_type is_container_impl(T);
template <class T>
struct is_container : decltype(is_container_impl<T>(declval<T>())) {};
template <>
struct is_container <string> : std::false_type {};
template <class Container, class = enable_if_t<is_container<Container>{}>>
istream& operator>> (istream& is, Container& cont) {
  for (auto& v : cont) is >> v;
  return is;
}
template <class Container, class = enable_if_t<is_container<Container>{}>>
ostream& operator<< (ostream& os, Container const& cont) {
  bool first = true;
  constexpr char sep =
    is_container<typename Container::value_type>{} ? '\n' : ' ';
  for (auto const& v : cont) {
    if (!first) {
      os << sep;
    }
    first = false;
    os << v;
  }
  return os;
}
// }}}
// }}}

struct edge {
  Z to;
  double cost;
};

using Graph = vector<vector<edge>>;

vector<double> dijkstra(Graph const& gr, Z start) {
  Z N = gr.size();
  vector<double> dists(N, 100000000000.0);
  priority_queue<pair<double, Z>, vector<pair<double, Z>>, greater<pair<double, Z>>> que;
  que.emplace(0, start);
  while (!que.empty()) {
    double d;
    Z v;
    tie(d, v) = que.top();
    que.pop();
    if (d >= ix(dists, v)) continue;
    ix(dists, v) = d;
    for (auto&& e : ix(gr, v)) {
      double nd = e.cost + d;
      if (nd >= ix(dists, e.to))
        continue;
      que.emplace(nd, e.to);
    }
  }
  return dists;
}

int main() {
  ios_base::sync_with_stdio(false);
  cin.tie(nullptr);
  cout.precision(10);
  cout << fixed;
  Z xs, ys, xt, yt, N;
  cin >> xs >> ys >> xt >> yt >> N;
  vector<Z> x(N + 2), y(N + 2), r(N + 2);
  for (auto i = 0; i < N; i++)
    cin >> ix(x, i) >> ix(y, i) >> ix(r, i);
  ix(x, N) = xs;
  ix(x, N + 1) = xt;
  ix(y, N) = ys;
  ix(y, N + 1) = yt;
  Graph gr(N + 2);
  for (auto i = 0; i < N + 2; i++) {
    for (auto j = 0; j < N + 2; j++) {
      if (i == j) continue;
      double dist = max(0., hypot(ix(x, i) - ix(x, j), ix(y, i) - ix(y, j)) - ix(r, i) - ix(r, j));
      ix(gr, i).push_back({j, dist});
    }
  }
  debug {
    for (auto&& row : gr) {
      for (auto&& e : row)
        cerr << '(' << e.to << ", " << e.cost << ") ";
      cerr << endl;
    }
  }
  auto const& ds = dijkstra(gr, N);
  dump(ds);
  cout << ix(ds, N + 1) << endl;
}



Measured memory_bytes: 26732