#define _USE_MATH_DEFINES
#include <iostream>
#include <fstream>
#include <cstdio>
#include <cmath>
#include <cstdlib>
#include <cstring>
#include <cassert>
#include <string>
#include <vector>
#include <utility>
#include <complex>
#include <set>
#include <map>
#include <queue>
#include <stack>
#include <deque>
#include <tuple>
#include <bitset>
#include <limits>
#include <algorithm>
#include <array>
#include <random>
#include <complex>
#include <regex>
using namespace std;
typedef long double ld;
typedef long long ll;
typedef vector<int> vint;
typedef vector<ll> vll;
typedef pair<int, int> pii;
typedef pair<ll, ll> pll;
typedef pair<double, double> pdd;
typedef complex<ld> compd;
#define quickIO()	{cin.tie(0);	cout.sync_with_stdio(false);}
#define reach(i,a)	for(auto i:a)
#define rep(i,n)	for(int i=0;i<(int)n;i++)
#define REP(i,n)	for(int i=0;i<=(int)n;i++)
#define srep(i,a,n)	for(int i=a;i<(int)n;i++)
#define SREP(i,a,n)	for(int i=a;i<=(int)n;i++)
#define rrep(i,n)	for(int i=n-1;i>=0;i--)
#define RREP(i,n)	for(int i=n;i>=0;i--)
#define all(a)	(a).begin(),(a).end()
#define mp(a,b)	make_pair(a,b)
#define mt	make_tuple
#define pb	push_back
#define fst	first
#define scn second
int bitcnt(ll x) {
	x = ((x & 0xAAAAAAAAAAAAAAAA) >> 1) + (x & 0x5555555555555555);
	x = ((x & 0xCCCCCCCCCCCCCCCC) >> 2) + (x & 0x3333333333333333);
	x = ((x & 0xF0F0F0F0F0F0F0F0) >> 4) + (x & 0x0F0F0F0F0F0F0F0F);
	x = ((x & 0xFF00FF00FF00FF00) >> 8) + (x & 0x00FF00FF00FF00FF);
	x = ((x & 0xFFFF0000FFFF0000) >> 16) + (x & 0x0000FFFF0000FFFF);
	x = ((x & 0xFFFFFFFF00000000) >> 32) + (x & 0x00000000FFFFFFFF);
	return x;
}
int bitcnt(int x) {
	x = ((x & 0xAAAAAAAA) >> 1) + (x & 0x55555555);
	x = ((x & 0xCCCCCCCC) >> 2) + (x & 0x33333333);
	x = ((x & 0xF0F0F0F0) >> 4) + (x & 0x0F0F0F0F);
	x = ((x & 0xFF00FF00) >> 8) + (x & 0x00FF00FF);
	x = ((x & 0xFFFF0000) >> 16) + (x & 0x0000FFFF);
	return x;
}
ll sqrt(ll x) {
	ll left = 0, right = x;
	rep(i, 100) {
		ll mid = (left + right) >> 1;
		if (mid*mid <= x)	left = mid;
		else	right = mid;
	}
	return left;
}
ll gcd(ll a, ll b) {
	return a%b == 0 ? b : gcd(b, a%b);
}
#define debug(x)	printf("Case #%d: ", x)
#define DEBUG 0
const ll inf = 1e18;
const ll mod = 1e9 + 7;
const ld eps = 1e-15;
const int dx[] = { 1,0,-1,0,0 };
const int dy[] = { 0,1,0,-1,0 };

ld dist[1000];

ld getdist(ll x, ll y, ll s, ll t) {
	return sqrtl((x - s)*(x - s) + (y - t)*(y - t));
}

int main() {
	pair<ll,ll> s, t;	cin >> s.first >> s.second >> t.first >> t.second;
	int n;	cin >> n;
	vector<tuple<ll, ll, ll>> barrier(n);
	rep(i, n) {
		ll x, y, r;	cin >> x >> y >> r;
		barrier[i] = mt(x, y, r);
	}
	priority_queue<pair<ld, int>> pq;
	ld ret = getdist(s.first, s.second, t.first, t.second);
	rep(i, n) {
		ld add = getdist(s.first, s.second, get<0>(barrier[i]), get<1>(barrier[i]));
		add = max(add - get<2>(barrier[i]), 0.0L);
		pq.push(mp(-add, i));
		dist[i] = add;
	}
	while (!pq.empty()) {
		auto it = pq.top();	pq.pop();
		ld curdist = -it.first;
		int cur = it.second;
		if (curdist - ret > eps)	break;
		if (curdist - dist[cur] > eps)	continue;
		ld tot = getdist(get<0>(barrier[cur]), get<1>(barrier[cur]), t.first, t.second);
		tot = max(tot - get<2>(barrier[cur]), 0.0L);
		ret = min(ret, dist[cur] + tot);
		rep(i, n) {
			ld add = getdist(get<0>(barrier[cur]), get<1>(barrier[cur]), get<0>(barrier[i]), get<1>(barrier[i]));
			add = max(add - get<2>(barrier[cur]) - get<2>(barrier[i]), 0.0L);
			if (dist[i] - dist[cur] - add > eps) {
				dist[i] = dist[cur] + add;
				pq.push(mp(-dist[i], i));
			}
		}
	}
	rep(i, n) {
		ld tot = getdist(get<0>(barrier[i]), get<1>(barrier[i]), t.first, t.second);
		tot = max(tot - get<2>(barrier[i]), 0.0L);
		ret = min(ret, dist[i] + tot);
	}
	printf("%.15Lf\n", ret);
	return 0;
}

Measured memory_bytes: 10096