#include <bits/stdc++.h>
 

//tabaicho  see https://boostjp.github.io/tips/multiprec-int.html   
// #include <boost/multiprecision/cpp_int.hpp>
// using namespace boost::multiprecision;

// cpp_int
// int128_t
// int256_t
// int512_t
// int1024_t

// uint128_t
// uint256_t
// uint512_t
// uint1024_t



 #define int long long
 #define inf  1000000007
// #define inf  998244353

 #define pa pair<int,int>
 #define ll long long
 #define PI 3.14159265358979323846
 #define  mp make_pair
 #define  pb push_back
 #define EPS (1e-8)
 
      using namespace std;
                                          
 int dx[8]={0,1,0,-1,1,1,-1,-1};
 int dy[8]={1,0,-1,0,-1,1,1,-1};
                                            
class pa3{
	public:
	int x;
	int y,z;
	pa3(int x=0,int y=0,int z=0):x(x),y(y),z(z) {}
	bool operator < (const pa3 &p) const{
		if(x!=p.x) return x<p.x;
		if(y!=p.y) return y<p.y;
		 return z<p.z;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator > (const pa3 &p) const{
		if(x!=p.x) return x>p.x;
		if(y!=p.y) return y>p.y;
		 return z>p.z;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa3 &p) const{
		return x==p.x && y==p.y && z==p.z;
	}
		bool operator != (const pa3 &p) const{
			return !( x==p.x && y==p.y && z==p.z);
	}

};

class pa4{
	public:
	int x;
	int y,z,w;
	pa4(int x=0,int y=0,int z=0,int w=0):x(x),y(y),z(z),w(w) {}
	bool operator < (const pa4 &p) const{
		if(x!=p.x) return x<p.x;
		if(y!=p.y) return y<p.y;
		if(z!=p.z)return z<p.z;
		return w<p.w;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator > (const pa4 &p) const{
		if(x!=p.x) return x>p.x;
		if(y!=p.y) return y>p.y;
		if(z!=p.z)return z>p.z;
		return w>p.w;
		//return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa4 &p) const{
		return x==p.x && y==p.y && z==p.z &&w==p.w;
	}
		

};
class pa2{
	public:
	int x,y;
	pa2(int x=0,int y=0):x(x),y(y) {}
	pa2 operator + (pa2 p) {return pa2(x+p.x,y+p.y);}
	pa2 operator - (pa2 p) {return pa2(x-p.x,y-p.y);}
	bool operator < (const pa2 &p) const{
		return y != p.y ? y<p.y: x<p.x;
	}
	bool operator > (const pa2 &p) const{
		return x != p.x ? x<p.x: y<p.y;
	}
	bool operator == (const pa2 &p) const{
		return abs(x-p.x)==0 && abs(y-p.y)==0;
	}
	bool operator != (const pa2 &p) const{
		return !(abs(x-p.x)==0 && abs(y-p.y)==0);
	}
		

};



string itos( int i ) {
	ostringstream s ;
	s << i ;
	return s.str() ;
}
 
int Gcd(int v,int b){
	if(v==0) return b;
	if(b==0) return v;
	if(v>b) return Gcd(b,v);
	if(v==b) return b;
	if(b%v==0) return v;
	return Gcd(v,b%v);
}


 int mod;
int extgcd(int a, int b, int &x, int &y) {
    if (b == 0) {
        x = 1;
        y = 0;
        return a;
    }
    int d = extgcd(b, a%b, y, x);
    y -= a/b * x;
    return d;
}
pa operator+(const pa & l,const pa & r) {   
    return {l.first+r.first,l.second+r.second};                                    
}    
pa operator-(const pa & l,const pa & r) {   
    return {l.first-r.first,l.second-r.second};                                    
}  

ostream& operator<<(ostream& os, const vector<int>& VEC){
	for(auto v:VEC)os<<v<<" ";
    return os;
}

ostream& operator<<(ostream& os, const pa& PAI){
	os<<PAI.first<<" : "<<PAI.second;
    return os;
}

ostream& operator<<(ostream& os, const pa3& PAI){
	os<<PAI.x<<" : "<<PAI.y<<" : "<<PAI.z;
    return os;
}

ostream& operator<<(ostream& os, const pa4& PAI){
	os<<PAI.x<<" : "<<PAI.y<<" : "<<PAI.z<<" : "<<PAI.y;
    return os;
}




int beki(int wa,int rr,int warukazu){
	if(rr==0) return 1%warukazu;
	if(rr==1) return wa%warukazu;
	wa%=warukazu;
	if(rr%2==1) return ((ll)beki(wa,rr-1,warukazu)*(ll)wa)%warukazu;
	ll zx=beki(wa,rr/2,warukazu);
	return (zx*zx)%warukazu;
}

              
int pr[1100000];
int inv[1100000];



int comb(int nn,int rr){
	if(rr<0 || rr>nn || nn<0) return 0;
	int r=pr[nn]*inv[rr];
	r%=mod;
	r*=inv[nn-rr];
	r%=mod;
	return r;
}

void gya(int ert){
	pr[0]=1;
	for(int i=1;i<=ert;i++){
		pr[i]=((ll)pr[i-1]*i)%mod;
	}
		inv[ert]=beki(pr[ert],mod-2,mod);
	for(int i=ert-1;i>=0;i--){
		inv[i]=(ll)inv[i+1]*(i+1)%mod;
	}
}


                


                
              //   cin.tie(0);
    		//	ios::sync_with_stdio(false);
    			//priority_queue<pa3,vector<pa3>,greater<pa3>> pq;            
                 //sort(ve.begin(),ve.end(),greater<int>());
 //   mt19937(clock_per_sec);
  //  mt19937_64 rng(chrono::steady_clock::now().time_since_epoch().count()) ;

struct fibonacci_heap{
	
	using Key=double;
	using Val=int;
	
	int sz=0;
	
	struct fh_node{
		int deg;
		bool cut;
		
		fh_node* prv;
		fh_node* nxt;
		fh_node* par;
		fh_node* chi;
		
		Key key;
		Val val;
		
		fh_node(){
			deg=0;
			cut=0;
			prv=nullptr;
			nxt=nullptr;
			par=nullptr;
			chi=nullptr;	
		}
		
		fh_node(Key k,Val v){
			deg=0;
			cut=0;
			prv=nullptr;
			nxt=nullptr;
			par=nullptr;
			chi=nullptr;	
			key=k;
			val=v;
		}
		
	};
	
	private:
	public:
	
	fh_node* deglist[100];
	
	fh_node* ROOT;
	/*
	map<Val,fh_node*> mp_node;
	
	fh_node* get_node(Val val){
		if(!mp_node.count(val)) return nullptr;
		return mp_node[val];
	}
	void set_node(Val val ,fh_node* node){
		mp_node[val]=node;
	}
	
	void unset_node(Val val){
		mp_node.erase(val);
	}
	*/
//	fh_node* mp_node[1020][1020];

	  vector<fh_node*>mp_node;
	fh_node* get_node(Val val){
		return mp_node[val];
	}
	void set_node(Val val ,fh_node* node){
		mp_node[val]=node;
	}
	
	void unset_node(Val val){
		mp_node[val]=nullptr;
	}
	
	
	fibonacci_heap(){
		ROOT = new fh_node;
		mp_node.resize(1010,nullptr);
		for(int i=0;i<100;i++)deglist[i]=nullptr;
	}
	
	// kirihanasu
	// node is not root of tree
	void make_new_tree(fh_node* node){
		fh_node* tmp=node->par;
		tmp->deg--;
		if(node->nxt==node){
			tmp->chi=nullptr;
		}
		else{
			if(tmp->chi==node)tmp->chi=node->nxt;
			
			node->nxt->prv=node->prv;
			node->prv->nxt=node->nxt;
		}
		
		node->par=ROOT;
		ROOT->chi->nxt->prv=node;
		node->nxt=ROOT->chi->nxt;
		ROOT->chi->nxt=node;
		node->prv=ROOT->chi;
		if(node->key<ROOT->chi->key)ROOT->chi=node;
		
	}
	
	void decrease_key(fh_node* node,Key key){
		node->key=key;
		if(node->par==ROOT){
			if(node->key<=ROOT->chi->key)ROOT->chi=node;
			return;
		}
		if(node->par->key<=key) return;
		
		fh_node* tmp=node->par;
		
		node->cut=0;
		
		make_new_tree(node);
		
		while(1){
			if(tmp->par==ROOT)break;
			if(tmp->cut==0){
				tmp->cut=1;
				break;
			}
			
			tmp->cut=0;
			node=tmp->par;
			make_new_tree(tmp);
			tmp=node;
		}
		
	}
	
	
	fh_node* merge(fh_node* v1,fh_node* v2){
		assert(v1->deg==v2->deg);
		if(v1->key>v2->key)swap(v1,v2);
		v1->deg++;
		if(v1->deg==1){
			v1->chi=v2;
			v2->nxt=v2;
			v2->prv=v2;
			v2->par=v1;
		}
		else{
			v1->chi->nxt->prv=v2;
			v2->nxt=v1->chi->nxt;
			v2->prv=v1->chi;
			v2->par=v1;
			v1->chi->nxt=v2;
			
		}
		return v1;
	}
	
	void merge_trees(){
		if(ROOT->chi==nullptr)return;
		
		fh_node* new_node=nullptr;
		fh_node* old_node=ROOT->chi;
		fh_node* tmp;
		
		old_node->prv->nxt=nullptr;
		
		while(1){
			tmp=old_node;
			old_node=old_node->nxt;
			
			if(new_node==nullptr){
				new_node=tmp;
				tmp->prv=nullptr;
				tmp->nxt=nullptr;
				deglist[tmp->deg]=tmp;
			}
			else{
				
				while(1){
					if(deglist[tmp->deg]==nullptr){
						deglist[tmp->deg]=tmp;
						tmp->nxt=new_node;
						tmp->prv=nullptr;
						if(new_node!=nullptr)new_node->prv=tmp;
						new_node=tmp;
						break;
					}
					
					fh_node* tmp2=deglist[tmp->deg];
					deglist[tmp->deg]=nullptr;
					
					if(tmp2->prv==nullptr && tmp2->nxt==nullptr){
						new_node=nullptr;
					}
					else if(tmp2->prv==nullptr){
						new_node=tmp2->nxt;
						tmp2->nxt->prv=nullptr;
					}
					else if(tmp2->nxt==nullptr){
						tmp2->prv->nxt=nullptr;
					}
					else{
						tmp2->prv->nxt=tmp2->nxt;
						tmp2->nxt->prv=tmp2->prv;
					}
					
					tmp=merge(tmp,tmp2);
				}
			}
			
			
			if(old_node==nullptr) break;
		}
		
		ROOT->chi=new_node;
		tmp=new_node;
		
		while(1){
			if(ROOT->chi->key>tmp->key){
				ROOT->chi=tmp;
			}
			deglist[tmp->deg]=nullptr;
			if(tmp->nxt==nullptr)break;
			tmp=tmp->nxt;
		}
		tmp->nxt=new_node;
		new_node->prv=tmp;
	}
	
	void push(Key key, Val val){
		
		
		
		fh_node* node=get_node(val);
		
		if(node!=nullptr){
			assert(node->key>=key);
			if(node->key>key)decrease_key(node,key);
		}
		else if(sz==0){
			sz++;
			node=new fh_node(key,val);
			ROOT->chi=node;
			node->prv=node;
			node->nxt=node;
			node->par=ROOT;
			set_node(val,node);
		}
		else{
			sz++;
			node=new fh_node(key,val);
			node->par=ROOT;
			node->prv=ROOT->chi;
			node->nxt=ROOT->chi->nxt;
			node->nxt->prv=node;
			ROOT->chi->nxt=node;
			if(ROOT->chi->key>key)ROOT->chi=node;
			set_node(val,node);
		}
		
	
	}
	
	pair<Key,Val> top(){
		assert(sz);
		return mp(ROOT->chi->key,ROOT->chi->val);
	}
	
	pair<Key,Val> pop(){
	
		assert(sz);	
		fh_node* erase_node=ROOT->chi;
		auto ans=mp(ROOT->chi->key,ROOT->chi->val);
		if(ROOT->chi->deg){
			fh_node* tmp =ROOT->chi->chi;
			while(tmp->par!=ROOT){
				tmp->par=ROOT;
				tmp=tmp->prv;
			}
			if(erase_node->prv==erase_node){
				ROOT->chi=tmp;
			}
			else{
				tmp->prv->nxt=erase_node->nxt;
				erase_node->nxt->prv=tmp->prv;
				erase_node->prv->nxt=tmp;
				tmp->prv=erase_node->prv;
				ROOT->chi=ROOT->chi->nxt;
			}
		}
		else{
			if(erase_node->prv==erase_node){
				ROOT->chi=nullptr;
		//		cout<<sz<<endl;
				assert(sz==1);
			}
			else{
				ROOT->chi=erase_node->prv;
				erase_node->prv->nxt=erase_node->nxt;
				erase_node->nxt->prv=erase_node->prv;
			}
		}
		sz--;
		
		merge_trees();
		
		unset_node(ans.second);
		delete erase_node;
	//	cout<<erase_node->key<<endl;
	//	cout<<ROOT->chi->key<<endl;
		
		
		//if(sz==14)exit(0);
		return ans;
	}
	
	void show(){
		show(ROOT);
	}
	
	void show(fh_node* node){
		if(node!=ROOT){
			if(node==ROOT->chi)cout<<"!!"<<endl;
			cout<<node->par->val<<" | "<<node->val<<" | "<<node->deg<<endl;
		}
		node=node->chi;
		if(node!=nullptr){
			if(node->par==ROOT || true){
			while(1){
				show(node);
				node=node->nxt;
				if(node->nxt==node->par->chi)break;
			}
			}
			else{
				int g=node->par->deg;
				for(int i=0;i<g;i++){
				show(node);
				node=node->nxt;
				//if(node->nxt==node->par->chi)break;
				}
			}
		}
	}
	
	int size(){
		return sz;
	}
};


double vis[1010];
bool sumi[1010]={};
double x[1010],y[1010],r[1010];

double d(int i,int j){
	double dx=x[i]-x[j];
	double dy=y[i]-y[j];
	double rr=r[i]+r[j];
	if(dx*dx+dy*dy<rr*rr)return 0;
	return sqrt(dx*dx+dy*dy)-rr;
}

void solve(){
	
	fibonacci_heap qu;
	cin>>x[0]>>y[0];
	r[0]=0;
	
	double X,Y;
	cin>>X>>Y;
	
	int n;
	cin>>n;
	x[n+1]=X;
	y[n+1]=Y;
	r[n+1]=0;
	
	
	for(int i=0;i<=n+1;i++)vis[i]=1e39;
	

	
	for(int i=1;i<=n;i++)cin>>x[i]>>y[i]>>r[i];
	
	qu.push(0.0,0);
	vis[0]=0;
	
	while(qu.size()){
		auto z=qu.pop();
		if(sumi[z.second])continue;
		
		sumi[z.second]=1;
		if(z.second==n+1){
			printf("%.10lf\n",z.first);
			return;
		}
	
		for(int i=0;i<=n+1;i++)if(!sumi[i])if(vis[i]>z.first){
			double f=d(z.second,i);
			if(vis[i]>z.first+f){
				vis[i]=z.first+f;
			
				qu.push(vis[i],i);
			}
		}
	}
	
}
 
signed main(){
	
	cin.tie(0);
	ios::sync_with_stdio(false);
int n=1;
	//cin>>n;
 
	
	for(int i=0;i<n;i++)solve();
	
	return 0;
 }

Measured memory_bytes: 3976