#define STOPIT
#include <bits/stdc++.h>
#define loop(n) for (int ngtkana_is_a_genius = 0; ngtkana_is_a_genius < int(n); ngtkana_is_a_genius++)
#define rep(i, begin, end) for (int i = int(begin); (i) < int(end); i++)
#define all(v) v.begin(), v.end()
#define rand(l, r) std::uniform_int_distribution<>(l, r)(mt)
using lint = long long;
auto mt = std::mt19937_64(std::random_device{}());
auto cmn = [](auto& a, auto b){ if (a > b) {a = b; return true;} return false; };
auto cmx = [](auto& a, auto b){ if (a < b) {a = b; return true;} return false; };
void debug_impl() { std::cerr << std::endl; }
template <typename Head, typename... Tail>
void debug_impl(Head head, Tail... tail) { std::cerr << " " << head; debug_impl(tail...); }
#ifndef STOPIT
#define debug(...)\
  do {\
    std::cerr << std::boolalpha << "[" << #__VA_ARGS__ << "]:";\
    debug_impl(__VA_ARGS__);\
    std::cerr << std::noboolalpha;\
  } while (false)
#else
#define debug(...) 0;
#endif

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr>
std::istream& operator>> (std::istream& is, Container& v)
  { for (auto & x : v) { is >> x; } return is; }

template < typename Container, typename Value = typename Container::value_type, std::enable_if_t<!std::is_same< Container, std::string >::value, std::nullptr_t> = nullptr >
std::ostream& operator<< (std::ostream& os, Container const& v) {
 os << "{";
  for (auto it = v.begin(); it != v.end(); it++)
    {os << (it != v.begin() ? "," : "") << *it;}
  return os << "}";
}

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& tuple_input_impl(std::istream& os, Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { (void)std::initializer_list<int>{((void)(os >> std::get< Inds >(tuple)), 0)...}; return os; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::istream& operator>> (std::istream& os, Tuple<Args...>& tuple)
  { return tuple_input_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < template < typename ... > class Tuple,  typename... Args, std::size_t ... Inds, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& tuple_output_impl(std::ostream& os, const Tuple<Args...>& tuple, std::integer_sequence<std::size_t, Inds...>)
  { os << "("; (void)std::initializer_list<int>{((void)(os << (Inds > 0 ? "," : "") << std::get< Inds >(tuple)), 0)...}; return os << ")"; }
template < template < typename ... > class Tuple,  typename... Args, std::size_t = std::tuple_size< Tuple < Args ... > >::value >
std::ostream& operator<< (std::ostream& os, const Tuple<Args...>& tuple)
 { return tuple_output_impl(os, tuple, std::index_sequence_for<Args...>()); }

template < typename Value >
auto dijkstra(std::vector< std::vector< std::pair< int, Value > > > const & graph, int start, Value inf) {
  // assert(2 * inf <= std::numeric_limits< Value >::max());
  std::vector< Value > dist(graph.size(), inf);
  std::priority_queue< std::pair< Value, int >,
    std::vector< std::pair< Value, int > >,
    std::greater< std::pair< Value, int > > > que;
  que.emplace(0, start);
  while (!que.empty()) {
    Value d; int crr; std::tie(d, crr) = que.top(); que.pop();
    if (dist.at(crr) <= d) continue;
    dist.at(crr) = d;
    for (auto pair : graph.at(crr)) {
      Value cost; int nxt; std::tie(nxt, cost) = pair;
      if (dist.at(nxt) - d <= cost) continue;
      que.emplace(d + cost, nxt);
    }
  }
  return dist;
}

int main() {
  std::cin.tie(0); std::cin.sync_with_stdio(false);
  double sx, sy, tx, ty;
  std::cin >> sx >> sy >> tx >> ty;
  int n; std::cin >> n;
  int N = n + 2;
  int s = n, t = n + 1;
  std::vector< std::tuple< double, double, double > > pts(n);
  std::cin >> pts;
  pts.emplace_back(sx,sy,0);
  pts.emplace_back(tx,ty,0);
  debug(pts);
  std::vector< std::vector< std::pair< int, double > > > graph(N);
  rep(i,0,N) rep(j,i+1,N) {
    double ix,iy,ir; std::tie(ix,iy,ir) = pts.at(i);
    double jx,jy,jr; std::tie(jx,jy,jr) = pts.at(j);
    double eu = std::hypot(ix-jx,iy-jy);
    debug(eu);
    double d = std::max(0., eu-ir-jr);
    debug(i,j,d);
    graph.at(i).emplace_back(j,d);
    graph.at(j).emplace_back(i,d);
  }
  debug(graph);

  double inf = std::numeric_limits< double >::infinity();
  auto dist = dijkstra< double >(graph, s, inf);
  debug(dist);
  double ans = dist.at(t);
  std::cout << std::setprecision(10) << ans << std::endl;
  return 0;
}

Measured memory_bytes: 26896