#include <bits/stdc++.h>
using namespace std;
#define int ll
#define ll long long
#define I32_MAX 2147483647
#define I64_MAX 9223372036854775807LL
#define I64_MAX2 1223372036854775807LL
#define INF I64_MAX2
#define MOD 1000000007
// #define MOD 998244353
#define MEM_SIZE 101010
#define DEBUG_OUT true
#define ALL(x) (x).begin(), (x).end()

template <typename T>
void DEBUG(T e)
{
  if (DEBUG_OUT == false)
    return;
  std::cout << e << " ";
}
template <typename T>
void DEBUG(const std::vector<T> &v)
{
  if (DEBUG_OUT == false)
    return;
  for (const auto &e : v)
  {
    std::cout << e << " ";
  }
  std::cout << std::endl;
}
template <typename T>
void DEBUG(const std::vector<std::vector<T>> &vv)
{
  if (DEBUG_OUT == false)
    return;
  for (const auto &v : vv)
  {
    DEBUG(v);
  }
}
template <class T, class... Ts>
void DEBUG(T d, Ts... e)
{
  if (DEBUG_OUT == false)
    return;
  DEBUG(d);
  DEBUG(e...);
}
template <class T>
void corner(bool flg, T hoge)
{
  if (flg)
  {
    cout << hoge << endl;
    abort();
  }
}
template <typename T1, typename T2>
inline bool chmax(T1 &a, T2 b) { return a < b && (a = b, true); }
template <typename T1, typename T2>
inline bool chmin(T1 &a, T2 b) { return a > b && (a = b, true); }

template <typename T>
struct edge
{
  int src, to;
  T cost;

  edge(int to, T cost) : src(-1), to(to), cost(cost) {}

  edge(int src, int to, T cost) : src(src), to(to), cost(cost) {}

  edge &operator=(const int &x)
  {
    to = x;
    return *this;
  }

  operator int() const { return to; }
};

template <typename T>
using Edges = vector<edge<T>>;
template <typename T>
using WeightedGraph = vector<Edges<T>>;
using UnWeightedGraph = vector<vector<int>>;
template <typename T>
using Matrix = vector<vector<T>>;

vector<double> dijkstra(WeightedGraph<double> &G, int s)
{

  vector<double> path(G.size(), std::numeric_limits<double>::max());
  path[s] = 0;
  priority_queue<pair<double, int>, vector<pair<double, int>>, greater<pair<double, int>>> que;

  que.emplace(path[s], s);

  while (!que.empty())
  {
    double cost;
    int idx;
    tie(cost, idx) = que.top();
    que.pop();

    if (path[idx] < cost)
      continue;
    for (auto &e : G[idx])
    {
      double next_cost = cost + e.cost;
      if (path[e.to] <= next_cost)
        continue;
      path[e.to] = next_cost;
      que.emplace(path[e.to], e.to);
    }
  }

  return path;
}

void solve(void)
{
  vector<tuple<int, int, int>> vt;
  int xx, yy, xxx, yyy;
  cin >> xx >> yy >> xxx >> yyy;
  vt.emplace_back(xx, yy, 0);
  vt.emplace_back(xxx, yyy, 0);

  int n;
  cin >> n;

  for (int i = 0; i < n; i++)
  {
    int a, b, c;
    cin >> a >> b >> c;
    vt.emplace_back(a, b, c);
  }
  WeightedGraph<double> WG(n + 2);
  for (int i = 0; i < n + 2; i++)
  {
    for (int j = 0; j < n + 2; j++)
    {
      if (i == j)
        continue;
      int x1, y1, r1;
      tie(x1, y1, r1) = vt[i];

      int x2, y2, r2;
      tie(x2, y2, r2) = vt[j];
      //i to j
      double cost = 0;
      cost = double(sqrt(double(x2 - x1) * (x2 - x1) + double(y2 - y1) * (y2 - y1))) - double(r1 + r2);
      if (cost < 0)
        cost = 0;
      // DEBUG(cost, t1, t2);
      WG[i].emplace_back(i, j, cost);
    }
  }

  // WeightedGraph<double> WG(n);
  // for (int i = 0; i < m; i++)
  // {
  //   int a, b, c;
  //   cin >> a >> b >> c;
  //   a--;
  //   b--;
  //   WG[a].emplace_back(a, b, c);
  //   WG[b].emplace_back(b, a, c);
  // }
  auto path = dijkstra(WG, 0);
  cout << path[1] << endl;
}
int32_t main(int32_t argc, const char *argv[])
{
  std::ios::sync_with_stdio(false);
  std::cin.tie(0);

  std::cout << std::fixed;
  std::cout << std::setprecision(11);
  solve();

  return 0;
}


Measured memory_bytes: 31508