#include <bits/stdc++.h>
using namespace std;

#define ms(s, n) memset(s, n, sizeof(s))
#define FOR(i, a, b) for (int i = (a); i < (b); i++)
#define FORd(i, a, b) for (int i = (a) - 1; i >= (b); i--)
#define FORall(it, a) for (__typeof((a).begin()) it = (a).begin(); it != (a).end(); it++)
#define sz(a) int((a).size())
#define present(t, x) (t.find(x) != t.end())
#define all(a) (a).begin(), (a).end()
#define uni(a) (a).erase(unique(all(a)), (a).end())
#define pb push_back
#define pf push_front
#define mp make_pair
#define fi first
#define se second
#define prec(n) fixed<<setprecision(n)
#define bit(n, i) (((n) >> (i)) & 1)
#define bitcount(n) __builtin_popcountll(n)
typedef long long ll;
typedef unsigned long long ull;
typedef long double ld;
typedef pair<int, int> pi;
typedef vector<int> vi;
typedef vector<pi> vii;
const int MOD = (int) 1e9 + 7;
const int INF = (int) 1e9;
const ll LINF = (ll) 1e18;
const ld PI = acos((ld) -1);
const ld EPS = 1e-9;
inline ll gcd(ll a, ll b) {ll r; while (b) {r = a % b; a = b; b = r;} return a;}
inline ll lcm(ll a, ll b) {return a / gcd(a, b) * b;}
inline ll fpow(ll n, ll k, int p = MOD) {ll r = 1; for (; k; k >>= 1) {if (k & 1) r = r * n % p; n = n * n % p;} return r;}
template<class T> inline int chkmin(T& a, const T& val) {return val < a ? a = val, 1 : 0;}
template<class T> inline int chkmax(T& a, const T& val) {return a < val ? a = val, 1 : 0;}
template<class T> inline T isqrt(T k) {T r = sqrt(k) + 1; while (r * r > k) r--; return r;}
template<class T> inline T icbrt(T k) {T r = cbrt(k) + 1; while (r * r * r > k) r--; return r;}
inline void addmod(int& a, int val, int p = MOD) {if ((a = (a + val)) >= p) a -= p;}
inline void submod(int& a, int val, int p = MOD) {if ((a = (a - val)) < 0) a += p;}
inline int mult(int a, int b, int p = MOD) {return (ll) a * b % p;}
inline int inv(int a, int p = MOD) {return fpow(a, p - 2, p);}

const int maxn = 1000 + 10;
int sx, sy, tx, ty;
int n;
int x[maxn];
int y[maxn];
int r[maxn];
vector<pair<int, long double> > adj[maxn];
long double d[maxn];

inline long long sqr(long long x) {return x * x;}

void solve() {
	cin >> sx >> sy >> tx >> ty;
	cin >> n;
	FOR(i, 0, n) cin >> x[i] >> y[i] >> r[i];
	long double dd = sqrt((long double) sqr(sx - tx) + sqr(sy - ty));
	adj[n].pb(mp(n + 1, dd));
	adj[n + 1].pb(mp(n, dd));
	FOR(i, 0, n) {
		long double d = sqrt((long double) sqr(sx - x[i]) + sqr(sy - y[i]));
		d -= r[i];
		if (d < 0) d = 0;
		adj[n].pb(mp(i, d));
		adj[i].pb(mp(n, d));
		d = sqrt((long double) sqr(tx - x[i]) + sqr(ty - y[i]));
		d -= r[i];
		if (d < 0) d = 0;
		adj[n + 1].pb(mp(i, d));
		adj[i].pb(mp(n + 1, d));
		FOR(j, i + 1, n) {
			long double d = sqrt((long double) sqr(x[i] - x[j]) + sqr(y[i] - y[j]));
			d -= r[i] + r[j];
			if (d < 0) d = 0;
			adj[i].pb(mp(j, d));
			adj[j].pb(mp(i, d));
		}
	}
	fill_n(d, n + 2, 1e18);
	d[n] = 0;
	priority_queue<pair<long double, int> > pq;
	pq.push(mp(-d[n], n));
	while (sz(pq)) {
		int u = pq.top().se;
		long double t = -pq.top().fi;
		pq.pop();
		if (fabs(d[u] - t) > EPS) continue;
		FOR(i, 0, sz(adj[u])) {
			int v = adj[u][i].fi;
			long double w = adj[u][i].se;
			if (d[v] > d[u] + w + EPS) {
				d[v] = d[u] + w;
				pq.push(mp(-d[v], v));
			}
		}
	}
	cout << prec(9) << d[n + 1] << "\n";
}

int main() {
	ios_base::sync_with_stdio(0); cin.tie(0);
#ifdef _LOCAL_
	freopen("in.txt", "r", stdin); //freopen("out.txt", "w", stdout);
#endif
	solve();
#ifdef _LOCAL_
	//printf("\nTime elapsed: %dms", 1000 * clock() / CLOCKS_PER_SEC);
#endif
	return 0;
}

Measured memory_bytes: 40976