import java.io.IOException;
import java.io.InputStream;
import java.io.OutputStream;
import java.io.PrintWriter;
import java.util.Arrays;
import java.util.NoSuchElementException;
import java.util.PriorityQueue;

/*
                   _ooOoo_
                  o8888888o
                  88" . "88
                  (| -_- |)
                  O\  =  /O
               ____/`---'\____
             .'  \\|     |//  `.
            /  \\|||  :  |||//  \
           /  _||||| -:- |||||-  \
           |   | \\\  -  /// |   |
           | \_|  ''\---/''  |   |
           \  .-\__  `-`  ___/-. /
         ___`. .'  /--.--\  `. . __
      ."" '<  `.___\_<|>_/___.'  >'"".
     | | :  `- \`.;`\ _ /`;.`/ - ` : | |
     \  \ `-.   \_ __\ /__ _/   .-` /  /
======`-.____`-.___\_____/___.-`____.-'======
                   `=---='
^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
            pass System Test!
*/

public class Main {
  private static class Task {
    class State implements Comparable<State> {
      int v;
      double cost;
      State(int v, double cost) {
        this.v = v;
        this.cost = cost;
      }

      @Override
      public int compareTo(State o) {
        if (this.cost > o.cost) return 1;
        if (this.cost < o.cost) return -1;
        return 0;
      }
    }
    void solve(FastScanner in, PrintWriter out) throws Exception {
      double xs = in.nextInt();
      double ys = in.nextInt();
      double xt = in.nextInt();
      double yt = in.nextInt();
      int N = in.nextInt();

      // N->N+1

      double[][] dist = new double[N + 2][N + 2];
      double[] x = new double[N + 2];
      double[] y = new double[N + 2];
      double[] r = new double[N + 2];
      for (int i = 0; i < N; i++) {
        x[i] = in.nextInt();
        y[i] = in.nextInt();
        r[i] = in.nextInt();
      }
      x[N] = xs;
      y[N] = ys;
      x[N + 1] = xt;
      y[N + 1] = yt;

      for (int i = 0; i < N + 2; i++) {
        for (int j = i + 1; j < N + 2; j++) {
          double dx = x[i] - x[j];
          double dy = y[i] - y[j];
          double d = Math.sqrt(dx * dx + dy * dy) - r[i] - r[j];
          d = Math.max(0, d);
          dist[i][j] = d;
          dist[j][i] = d;
        }
      }

      double[] costs = new double[N + 2];
      Arrays.fill(costs, 1e14);
      PriorityQueue<State> queue = new PriorityQueue<>();
      costs[N] = 0.0;
      queue.add(new State(N, 0.0));

      boolean[] vis = new boolean[N + 2];
      while (!queue.isEmpty()) {
        State state = queue.poll();
        int v = state.v;

        if (v == N + 1) {
          out.println(costs[N + 1]);
          return;
        }

        if (vis[v]) continue;
        vis[v] = true;
        for (int i = 0; i < N + 2; i++) {
          if (v == i) continue;
          if (costs[i] <= costs[v] + dist[v][i]) continue;
          costs[i] = costs[v] + dist[v][i];
          queue.add(new State(i, costs[i]));
        }
      }

    }
  }

  /**
   * ここから下はテンプレートです。
   */
  public static void main(String[] args) throws Exception {
    OutputStream outputStream = System.out;
    FastScanner in = new FastScanner();
    PrintWriter out = new PrintWriter(outputStream);
    Task solver = new Task();
    solver.solve(in, out);
    out.close();
  }

  private static class FastScanner {
    private final InputStream in = System.in;
    private final byte[] buffer = new byte[1024];
    private int ptr = 0;
    private int bufferLength = 0;

    private boolean hasNextByte() {
      if (ptr < bufferLength) {
        return true;
      } else {
        ptr = 0;
        try {
          bufferLength = in.read(buffer);
        } catch (IOException e) {
          e.printStackTrace();
        }
        if (bufferLength <= 0) {
          return false;
        }
      }
      return true;
    }

    private int readByte() {
      if (hasNextByte()) return buffer[ptr++];
      else return -1;
    }

    private static boolean isPrintableChar(int c) {
      return 33 <= c && c <= 126;
    }

    private void skipUnprintable() {
      while (hasNextByte() && !isPrintableChar(buffer[ptr])) ptr++;
    }

    boolean hasNext() {
      skipUnprintable();
      return hasNextByte();
    }

    public String next() {
      if (!hasNext()) throw new NoSuchElementException();
      StringBuilder sb = new StringBuilder();
      int b = readByte();
      while (isPrintableChar(b)) {
        sb.appendCodePoint(b);
        b = readByte();
      }
      return sb.toString();
    }

    long nextLong() {
      if (!hasNext()) throw new NoSuchElementException();
      long n = 0;
      boolean minus = false;
      int b = readByte();
      if (b == '-') {
        minus = true;
        b = readByte();
      }
      if (b < '0' || '9' < b) {
        throw new NumberFormatException();
      }
      while (true) {
        if ('0' <= b && b <= '9') {
          n *= 10;
          n += b - '0';
        } else if (b == -1 || !isPrintableChar(b)) {
          return minus ? -n : n;
        } else {
          throw new NumberFormatException();
        }
        b = readByte();
      }
    }

    double nextDouble() {
      return Double.parseDouble(next());
    }

    double[] nextDoubleArray(int n) {
      double[] array = new double[n];
      for (int i = 0; i < n; i++) {
        array[i] = nextDouble();
      }
      return array;
    }

    double[][] nextDoubleMap(int n, int m) {
      double[][] map = new double[n][];
      for (int i = 0; i < n; i++) {
        map[i] = nextDoubleArray(m);
      }
      return map;
    }

    public int nextInt() {
      return (int) nextLong();
    }

    public int[] nextIntArray(int n) {
      int[] array = new int[n];
      for (int i = 0; i < n; i++) array[i] = nextInt();
      return array;
    }

    public long[] nextLongArray(int n) {
      long[] array = new long[n];
      for (int i = 0; i < n; i++) array[i] = nextLong();
      return array;
    }

    public String[] nextStringArray(int n) {
      String[] array = new String[n];
      for (int i = 0; i < n; i++) array[i] = next();
      return array;
    }

    public char[][] nextCharMap(int n) {
      char[][] array = new char[n][];
      for (int i = 0; i < n; i++) array[i] = next().toCharArray();
      return array;
    }

    public int[][] nextIntMap(int n, int m) {
      int[][] map = new int[n][];
      for (int i = 0; i < n; i++) {
        map[i] = nextIntArray(m);
      }
      return map;
    }
  }
}

Measured memory_bytes: 39492