using System;
using System.Collections.Generic;
using System.Linq;
using System.IO;
using System.Threading;
using System.Text;
using System.Diagnostics;
using static util;
using P = pair<int, int>;
using Number = System.Double;

class Program {
    static void Main(string[] args) {
        var sw = new StreamWriter(Console.OpenStandardOutput()) { AutoFlush = false };
        var solver = new Solver(sw);
        // var t = new Thread(solver.solve, 1 << 26); // 64 MB
        // t.Start();
        // t.Join();
        solver.solve();
        sw.Flush();
    }
}

class Solver {
    StreamWriter sw;
    Scan sc;
    void Prt(string a) => sw.WriteLine(a);
    void Prt<T>(IEnumerable<T> a) => Prt(string.Join(" ", a));
    void Prt(params object[] a) => Prt(string.Join(" ", a));
    public Solver(StreamWriter sw) {
        this.sw = sw;
        this.sc = new Scan();
    }

    public void solve() {
        int sx, sy, gx, gy;
        sc.Multi(out sx, out sy, out gx, out gy);
        int n = sc.Int;
        var p = new int[n + 2][];
        for (int i = 0; i < n; i++)
        {
            p[i] = sc.IntArr;
        }
        n += 2;
        p[n - 2] = new int[]{ sx, sy, 0 };
        p[n - 1] = new int[]{ gx, gy, 0 };
        var edge = new List<pair<double, int>>[n];
        for (int i = 0; i < n; i++)
        {
            edge[i] = new List<pair<double, int>>();
            for (int j = 0; j < n; j++)
            {
                if (i == j) continue;
                double c = Math.Max(Math.Sqrt((p[i][0] - p[j][0]) * (double)(p[i][0] - p[j][0]) + (p[i][1] - p[j][1]) * (double)(p[i][1] - p[j][1])) - p[i][2] - p[j][2], 0);
                edge[i].Add(new pair<double, int>(c, j));
            }
        }
        Prt(ShortestPath.Dijkstra(edge, n - 2)[n - 1]);
    }
}

class pair<T, U> : IComparable<pair<T, U>> {
    public T v1;
    public U v2;
    public pair() : this(default(T), default(U)) {}
    public pair(T v1, U v2) { this.v1 = v1; this.v2 = v2; }
    public int CompareTo(pair<T, U> a) {
        int c = Comparer<T>.Default.Compare(v1, a.v1);
        return c != 0 ? c : Comparer<U>.Default.Compare(v2, a.v2);
    }
    public override string ToString() => v1 + " " + v2;
    public void Deconstruct(out T a, out U b) { a = v1; b = v2; }
}
static class util {
    public static readonly int M = 1000000007;
    // public static readonly int M = 998244353;
    public static readonly long LM = 1L << 60;
    public static readonly double eps = 1e-11;
    public static void DBG(string a) => Console.Error.WriteLine(a);
    public static void DBG<T>(IEnumerable<T> a) => DBG(string.Join(" ", a));
    public static void DBG(params object[] a) => DBG(string.Join(" ", a));
    public static void Assert(bool cond) { if (!cond) throw new Exception(); }
    public static pair<T, U> make_pair<T, U>(T v1, U v2) => new pair<T, U>(v1, v2);
    public static int CompareList<T>(IList<T> a, IList<T> b) where T : IComparable<T> {
        for (int i = 0; i < a.Count && i < b.Count; i++)
            if (a[i].CompareTo(b[i]) != 0) return a[i].CompareTo(b[i]);
        return a.Count.CompareTo(b.Count);
    }
    public static bool inside(int i, int j, int h, int w) => i >= 0 && i < h && j >= 0 && j < w;
    static readonly int[] dd = { 0, 1, 0, -1 };
    // static readonly string dstring = "RDLU";
    public static P[] adjacents(int i, int j)
        => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1])).ToArray();
    public static P[] adjacents(int i, int j, int h, int w)
        => Enumerable.Range(0, dd.Length).Select(k => new P(i + dd[k], j + dd[k ^ 1]))
                                         .Where(p => inside(p.v1, p.v2, h, w)).ToArray();
    public static P[] adjacents(this P p) => adjacents(p.v1, p.v2);
    public static P[] adjacents(this P p, int h, int w) => adjacents(p.v1, p.v2, h, w);
    public static Dictionary<T, int> compress<T>(this IEnumerable<T> a)
        => a.Distinct().OrderBy(v => v).Select((v, i) => new { v, i }).ToDictionary(p => p.v, p => p.i);
    public static Dictionary<T, int> compress<T>(params IEnumerable<T>[] a) => compress(a.Aggregate(Enumerable.Union));
    public static T[] inv<T>(this Dictionary<T, int> dic) {
        var res = new T[dic.Count];
        foreach (var item in dic) res[item.Value] = item.Key;
        return res;
    }
    public static void swap<T>(ref T a, ref T b) where T : struct { var t = a; a = b; b = t; }
    public static void swap<T>(this IList<T> a, int i, int j) where T : struct { var t = a[i]; a[i] = a[j]; a[j] = t; }
    public static T[] copy<T>(this IList<T> a) {
        var ret = new T[a.Count];
        for (int i = 0; i < a.Count; i++) ret[i] = a[i];
        return ret;
    }
}

class Scan {
    StreamReader sr;
    public Scan() { sr = new StreamReader(Console.OpenStandardInput()); }
    public Scan(string path) { sr = new StreamReader(path); }
    public int Int => int.Parse(Str);
    public long Long => long.Parse(Str);
    public double Double => double.Parse(Str);
    public string Str => sr.ReadLine().Trim();
    public pair<T, U> Pair<T, U>() {
        T a; U b;
        Multi(out a, out b);
        return new pair<T, U>(a, b);
    }
    public P P => Pair<int, int>();
    public int[] IntArr => StrArr.Select(int.Parse).ToArray();
    public long[] LongArr => StrArr.Select(long.Parse).ToArray();
    public double[] DoubleArr => StrArr.Select(double.Parse).ToArray();
    public string[] StrArr => Str.Split(new[]{' '}, StringSplitOptions.RemoveEmptyEntries);
    bool eq<T, U>() => typeof(T).Equals(typeof(U));
    T ct<T, U>(U a) => (T)Convert.ChangeType(a, typeof(T));
    T cv<T>(string s) => eq<T, int>()    ? ct<T, int>(int.Parse(s))
                       : eq<T, long>()   ? ct<T, long>(long.Parse(s))
                       : eq<T, double>() ? ct<T, double>(double.Parse(s))
                       : eq<T, char>()   ? ct<T, char>(s[0])
                                         : ct<T, string>(s);
    public void Multi<T>(out T a) => a = cv<T>(Str);
    public void Multi<T, U>(out T a, out U b)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); }
    public void Multi<T, U, V>(out T a, out U b, out V c)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); }
    public void Multi<T, U, V, W>(out T a, out U b, out V c, out W d)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); }
    public void Multi<T, U, V, W, X>(out T a, out U b, out V c, out W d, out X e)
    { var ar = StrArr; a = cv<T>(ar[0]); b = cv<U>(ar[1]); c = cv<V>(ar[2]); d = cv<W>(ar[3]); e = cv<X>(ar[4]); }
}


static class ShortestPath {
    static Number Inf = util.LM;
    public static void WarshallFloyd(Number[][] g) {
        int n = g.Length;
        for (int i = 0; i < n; ++i)
            for (int j = 0; j < n; ++j)
                for (int k = 0; k < n; ++k)
                    g[j][k] = Math.Min(g[j][k], g[j][i] + g[i][k]);
    }
    class Heap {
        int n;
        Number[] values;
        int[] keys, indices;
        public Heap(Number[] dist) {
            n = dist.Length;
            values = dist;
            keys = new int[n];
            for (int i = 0; i < n; i++) {
                keys[i] = i;
            }
            Array.Sort(keys, (x, y) => values[x].CompareTo(values[y]));
            indices = new int[n];
            for (int i = 0; i < n; i++) {
                indices[keys[i]] = i;
            }
        }
        void swap(int i, int j) {
            int t = keys[i]; keys[i] = keys[j]; keys[j] = t;
            indices[keys[i]] = i;
            indices[keys[j]] = j;
        }
        // int cmp(int i, int j) => values[keys[i]] > values[keys[j]] ? 1 : values[keys[i]] < values[keys[j]] ? -1 : 0;
        int cmp(int i, int j) => values[keys[i]].CompareTo(values[keys[j]]);

        // value[i] > a
        public void Update(int i, Number a) {
            values[i] = a;
            int j = indices[i];
            while (j > 0) {
                int k = (j - 1) >> 1;
                if (cmp(j, k) >= 0) break;
                swap(j, k);
                j = k;
            }
        }
        public int Pop() {
            --n;
            swap(0, n);
            int ret = keys[n];
            keys[n] = -1;
            indices[ret] = -1;
            for (int i = 0, j; (j = i << 1 | 1) < n; i = j) {
                if (j != n - 1 && cmp(j, j + 1) > 0) ++j;
                if (cmp(i, j) > 0) swap(i, j);
                else break;
            }
            return ret;
        }
        public int Top => keys[0];
        // public int Count => n;
    }


    public static Number[] Dijkstra(List<pair<Number, int>>[] edges, int s) {
        int n = edges.Length;
        var dist = new Number[n];
        for (int i = 0; i < n; ++i) dist[i] = Inf;
        dist[s] = 0;
        var q = new Heap(dist);
        while (q.Top != -1 && dist[q.Top] < Inf) {
            int p = q.Pop();
            foreach (var e in edges[p]) {
                Number d = dist[p] + e.v1;
                if (dist[e.v2] > d) {
                    q.Update(e.v2, d);
                }
            }
        }
        return dist;
    }
    public static Number[] Dijkstra(List<pair<Number, int>>[] edges, Number[] dist) {
        int n = edges.Length;
        var q = new Heap(dist);
        while (q.Top != -1 && dist[q.Top] < Inf) {
            int p = q.Pop();
            foreach (var e in edges[p]) {
                Number d = dist[p] + e.v1;
                if (dist[e.v2] > d) {
                    q.Update(e.v2, d);
                }
            }
        }
        return dist;
    }
    // public static Number[] Dijkstra(List<pair<Number, int>>[] edges, int s, out long[] cnt, long Mod) {
    //     int n = edges.Length;
    //     var dist = new Number[n];
    //     var q = new PriorityQueue<pair<Number, int>>(){ rev = true };
    //     for (int i = 0; i < n; ++i) dist[i] = Inf;
    //     dist[s] = 0;
    //     q.Push(new pair<Number, int>(dist[s], s));
    //     cnt = new long[n];
    //     cnt[s] = 1;
    //     while (q.Count > 0) {
    //         var p = q.Pop();
    //         if (dist[p.v2] < p.v1) continue;
    //         foreach (var e in edges[p.v2]) {
    //             Number d = p.v1 + e.v1;
    //             if (dist[e.v2] > d) {
    //                 dist[e.v2] = d;
    //                 cnt[e.v2] = cnt[p.v2];
    //                 q.Push(new pair<Number, int>(d, e.v2));
    //             }
    //             else if (dist[e.v2] == d) cnt[e.v2] = (cnt[e.v2] + cnt[p.v2]) % Mod;
    //         }
    //     }
    //     return dist;
    // }
}


Measured memory_bytes: 61740