#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <cmath>
#include <climits>
#include <cfloat>
#include <ctime>
#include <cassert>
#include <map>
#include <utility>
#include <set>
#include <iostream>
#include <memory>
#include <string>
#include <vector>
#include <algorithm>
#include <functional>
#include <sstream>
#include <complex>
#include <stack>
#include <queue>
#include <numeric>
#include <list>
#include <iomanip>
#include <fstream>
#include <bitset>

using namespace std;

#define foreach(it, c) for (__typeof__((c).begin()) it=(c).begin(); it != (c).end(); ++it)
template <typename T> void print_container(ostream& os, const T& c) { const char* _s = " "; if (!c.empty()) { __typeof__(c.begin()) last = --c.end(); foreach (it, c) { os << *it; if (it != last) os << _s; } } }
template <typename T> ostream& operator<<(ostream& os, const vector<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const set<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const multiset<T>& c) { print_container(os, c); return os; }
template <typename T> ostream& operator<<(ostream& os, const deque<T>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const map<T, U>& c) { print_container(os, c); return os; }
template <typename T, typename U> ostream& operator<<(ostream& os, const pair<T, U>& p) { os << "(" << p.first << ", " << p.second << ")"; return os; }

template <typename T> void print(T a, int n, const string& split = " ") { for (int i = 0; i < n; i++) { cout << a[i]; if (i + 1 != n) cout << split; } cout << endl; }
template <typename T> void print2d(T a, int w, int h, int width = -1, int br = 0) { for (int i = 0; i < h; ++i) { for (int j = 0; j < w; ++j) { if (width != -1) cout.width(width); cout << a[i][j] << ' '; } cout << endl; } while (br--) cout << endl; }
template <typename T> void input(T& a, int n) { for (int i = 0; i < n; ++i) cin >> a[i]; }
#define dump(v) (cout << #v << ": " << v << endl)

#define rep(i, n) for (int i = 0; i < (int)(n); ++i)
#define erep(i, n) for (int i = 0; i <= (int)(n); ++i)
#define all(a) (a).begin(), (a).end()
#define rall(a) (a).rbegin(), (a).rend()
#define clr(a, x) memset(a, x, sizeof(a))
#define sz(a) ((int)(a).size())
#define mp(a, b) make_pair(a, b)
#define ten(n) ((long long)(1e##n))

template <typename T, typename U> void upmin(T& a, const U& b) { a = min<T>(a, b); }
template <typename T, typename U> void upmax(T& a, const U& b) { a = max<T>(a, b); }
template <typename T> void uniq(T& a) { sort(a.begin(), a.end()); a.erase(unique(a.begin(), a.end()), a.end()); }
template <class T> string to_s(const T& a) { ostringstream os; os << a; return os.str(); }
template <class T> T to_T(const string& s) { istringstream is(s); T res; is >> res; return res; }
void fast_io() { cin.tie(0); ios::sync_with_stdio(false); }
bool in_rect(int x, int y, int w, int h) { return 0 <= x && x < w && 0 <= y && y < h; }

typedef long long ll;
typedef pair<int, int> pint;

const int dx[] = { 0, 1, 0, -1 };
const int dy[] = { 1, 0, -1, 0 };


double dist(double x1, double y1, double x2, double y2) {
    double dx = x1 - x2;
    double dy = y1 - y2;
    return sqrt(dx * dx + dy * dy);
}
int main() {
    double sx, sy, gx, gy;
    cin >> sx >> sy >> gx >> gy;
    int n;
    cin >> n;

    double cx[1024], cy[1024], r[1024];
    rep(i, n)
        cin >> cx[i] >> cy[i] >> r[i];
    cx[n] = sx;
    cy[n] = sy;
    r[n] = 0;
    cx[n + 1] = gx;
    cy[n + 1] = gy;
    r[n + 1] = 0;

    static double g[1024][1024];
    rep(i, n + 2) rep(j, n + 2) {
        // printf("%d %d: %.5f\n", i, j, dist(cx[i], cy[i], cx[j], cy[j]) - (r[i] + r[j]));
        g[i][j] = max(0.0, dist(cx[i], cy[i], cx[j], cy[j]) - (r[i] + r[j]));
    }

    using P = pair<double, int>;
    vector<double> dp(n + 2, 1e60);
    priority_queue<P, vector<P>, greater<P>> q;
    dp[n] = 0;
    q.push(P(0, n));
    while (!q.empty()) {
        const double cost = q.top().first;
        const int cur = q.top().second;
        q.pop();

        if (cost > dp[cur])
            continue;

        rep(to, n + 2) {
            const double ncost = cost + g[cur][to];
            if (ncost < dp[to]) {
                dp[to] = ncost;
                q.push(P(ncost, to));
            }
        }
    }
    // print2d(g, n + 2, n + 2);
    // dump(dp);
    printf("%.10f\n", dp[n + 1]);
}


Measured memory_bytes: 12532