// **** WHEN THE GOING GETS TOUGH, THE TOUGH GETS GOING. ****

#include <bits/stdc++.h>
#include <ext/pb_ds/assoc_container.hpp>
#include <ext/pb_ds/tree_policy.hpp>
using namespace __gnu_pbds;
using namespace std;
#define ll long long int
#define ull unsigned long long int
#define ld long double
#define ordered_set tree < ll ,  null_type ,  less<ll> ,  rb_tree_tag ,  tree_order_statistics_node_update >
//added two more functions to set
//(1)*(set.find_by_order(k))[kth element in the sorted set] 
//(2)set.order_of_key(k)[count of elements strictly less than k]

typedef vector< int > vi;
typedef vector< ll > lvi;
typedef vector< vi > vvi;
typedef vector< lvi > lvvi;
typedef pair< int,int > ii;
typedef pair< ll,ll > lii;
typedef vector<ii> vii;
typedef vector<lii> lvii;

#define min_prq(t) priority_queue<t,vector<t>,greater<t>>
#define max_prq(t) priority_queue<t>
#define pb push_back
#define all(c) (c).begin(),(c).end()
#define tr(c,i) for(auto i = (c).begin(); i != (c).end(); i++)//remember i is an iterator
#define present(c,x) ((c).find(x) != (c).end())//for sets,maps,multimaps
#define cpresent(c,x) (find(all(c),x) != (c).end())//for vectors
#define tc(t) int (t); cin>>(t);while((t)--)
#define x first
#define y second
#define error(args...) { string _s = #args; replace(_s.begin(), _s.end(), ',', ' '); stringstream _ss(_s); istream_iterator<string> _it(_ss); err(_it, args); }
void err(istream_iterator<string> it) {}
template<typename T, typename... Args>
void err(istream_iterator<string> it, T a, Args... args) {
	cerr << *it << " is " << a << endl;
	err(++it, args...);
}

//-----------------------------------------------------------------------------------------------------------------------------------------------------------------
#define mod 1000000007
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------

ll mod_sum() { return 0LL; }
template<typename T, typename... Args>
T mod_sum(T a, Args... args) { return ((a + mod_sum(args...))%mod + mod)%mod; }

ll mod_product() { return 1LL; }
template<typename T, typename... Args>
T mod_product(T a, Args... args) { return (a*mod_product(args...))%mod; }
//-----------------------------------------------------------------------------------------------------------------------------------------------------------------

const ll inf=1e15;

ld dist(lii src,lii dst,ll sub=0)
{
	ld dt=(src.x-dst.x)*(src.x-dst.x)+(src.y-dst.y)*(src.y-dst.y);
	dt=sqrt(dt);
	dt-=sub;
	if(dt<0) dt=0;
	return dt;
}

vector<ld> dis;
map<lii,ll>  mp;
vector<lii> cr;
lvi rad;
lii src,dst;
ll n;

void dks()
{
	dis.assign(n+3,inf);
	dis[0]=0;
	priority_queue<pair<ld,ll>,vector<pair<ld,ll>>,greater<pair<ld,ll>>> q;
	q.push({0,0});
	while(!q.empty())
	{
		ll curr=q.top().y;
		ld d_v=q.top().x;
		q.pop();
		if(d_v!=dis[curr]) continue;
		for(int i=0;i<n+2;i++)
		{
			if(curr==i) continue;
			ld extra=dist(cr[curr],cr[i],rad[i]+rad[curr]);
			if((extra+dis[curr])<dis[i])
			{
				dis[i]=extra+dis[curr];
				q.push({dis[i],i});
			}
		}
	}

}

signed main()
{
	ios_base::sync_with_stdio(false);
    cin.tie(NULL);	
	cin>>src.x>>src.y>>dst.x>>dst.y;
	cin>>n;
	rad.assign(n+3,0);
	mp[src]=0;
	cr.pb(src);
	rad[0]=0;
	mp[dst]=1;
	cr.pb(dst);
	rad[1]=0;
	for (int i = 2; i < n+2; ++i)
	{
		ll x,y,r;
		cin>>x>>y>>r;
		cr.pb({x,y});
		mp[{x,y}]=i;
		rad[i]=r;
	}
	dks();
	cout<<fixed<<setprecision(12)<<dis[1]<<endl;
	return 0;
}

Measured memory_bytes: 10476