#![allow(unused_imports, unused_macros, unknown_lints)]

use std::collections::*;
use std::f64::*;
use std::cmp::*;
use std::cmp::Ordering::*;

macro_rules! dump {($($e:expr), +) => {print!(concat!($(stringify!($e), " = {:?}\n"), +), $($e), +)}}

fn main() {
  let (xs,ys,xt,yt) = {
    let vec = get::vec::<f64>();
    (vec[0], vec[1], vec[2], vec[3])
  };
  let n = get::val::<usize>();
  let mut xyrs = get::tuple3s::<f64,f64,f64>(n);
  xyrs.push((xs,ys,0.0));
  xyrs.push((xt,yt,0.0));
  
  let dist = |(xi,yi,ri),(xj,yj,rj)| {
    f64::sqrt((xj-xi)*(xj-xi)+(yj-yi)*(yj-yi)) - ri - rj
  };
  
  let mut es = vec![];
  for i in 0 .. n+2 {
    for j in 0 .. n+2 {
      if i == j {continue}
      es.push((i,j,f64::max(0.0,dist(xyrs[i],xyrs[j]))))
    }
  }
  
  let mut g = vec![vec![]; n+2];
  for (u,v,c) in es {g[u].push((v,c))}

  let mut dk = vec![None; n+2];
  dk[n] = Some(0.0);
  
  let mut pq = BinaryHeap::new();
  pq.push((F64Total(0.0),n));
  while let Some((F64Total(d),v)) = pq.pop() {
    let d = -d;
    for &(w,c) in &g[v] {
      match dk[w] {
        Some(d0) if d0 <= d+c => {continue},
        _ => {dk[w] = Some(d+c); pq.push((F64Total(-(d+c)),w))}
      }
    }
  }
   
  println!("{}", dk[n+1].unwrap())
}

#[derive(PartialEq, PartialOrd)]
struct F64Total(f64);

impl Eq for F64Total {}
impl Ord for F64Total {
  fn cmp(&self, other: &F64Total) -> Ordering {
    let F64Total(f1) = *self;
    let F64Total(f2) = *other;
    if f1.is_nan() {
      Less
    } else if f2.is_nan() {
      Greater
    } else {
      if (f1-f2).is_sign_positive() {Greater} else {Less}
    }
  }
}

#[allow(dead_code)]
mod get {
  use std::io::*;
  use std::str::*;
  use std::process::*;

  pub fn val<T: FromStr>() -> T {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    if buf.is_empty() {println!("No input"); exit(0)}
    buf.trim_right().parse::<T>().ok().unwrap()
  }

  pub fn vals<T: FromStr>(n: usize) -> Vec<T> {
    let mut vec: Vec<T> = vec![];
    for _ in 0 .. n {
      vec.push(val());
    }
    vec
  }

  pub fn tuple<T1: FromStr, T2: FromStr>() -> (T1, T2) {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    if buf.is_empty() {println!("No input"); exit(0)}
    let mut it = buf.trim_right().split_whitespace();
    let x = it.next().unwrap().parse::<T1>().ok().unwrap();
    let y = it.next().unwrap().parse::<T2>().ok().unwrap();
    (x, y)
  }

  pub fn tuples<T1: FromStr, T2: FromStr>(n: usize) -> Vec<(T1, T2)> {
    let mut vec: Vec<(T1, T2)> = vec![];
    for _ in 0 .. n {
      vec.push(tuple());
    }
    vec
  }

  pub fn tuple3<T1: FromStr, T2: FromStr, T3: FromStr>() -> (T1, T2, T3) {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    if buf.is_empty() {println!("No input"); exit(0)}
    let mut it = buf.trim_right().split_whitespace();
    let x = it.next().unwrap().parse::<T1>().ok().unwrap();
    let y = it.next().unwrap().parse::<T2>().ok().unwrap();
    let z = it.next().unwrap().parse::<T3>().ok().unwrap();
    (x, y, z)
  }

  pub fn tuple3s<T1: FromStr, T2: FromStr, T3: FromStr>(n: usize) -> Vec<(T1, T2, T3)> {
    let mut vec: Vec<(T1, T2, T3)> = vec![];
    for _ in 0 .. n {
      vec.push(tuple3());
    }
    vec
  }

  pub fn vec<T: FromStr>() -> Vec<T> {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    if buf.is_empty() {println!("No input"); exit(0)}
    buf.trim_right().split_whitespace().map(|t| t.parse::<T>().ok().unwrap()).collect()
  }

  pub fn mat<T: FromStr>(h: usize) -> Vec<Vec<T>> {
    let mut mat = vec![];
    for _ in 0 .. h {
      mat.push(vec());
    }
    mat
  }

  pub fn chars() -> Vec<char> {
    let mut buf = String::new();
    let s = stdin();
    s.lock().read_line(&mut buf).ok();
    if buf.is_empty() {println!("No input"); exit(0)}
    buf.trim_right().chars().collect()
  }
}

#[allow(dead_code)]
mod put {
  use std::string::*;

  pub fn vec<T: ToString>(vec: &Vec<T>, sep: &str) {
    let out = vec.iter().map(|e| e.to_string()).collect::<Vec<_>>().as_slice().join(sep);
    println!("{}", out);
  }

  pub fn mat<T: ToString>(mat: &Vec<Vec<T>>, sep: &str) {
    for v in mat {
      vec(v, sep);
    }
  }
}


Measured memory_bytes: 49268