#include <bits/stdc++.h> // ver2.7.1
#define int long long
#define endl "\n" // fflush(stdout);
#define ALL(v) (v).begin(),(v).end()
#define Vi vector<int>
#define VVi vector<Vi>
#define VVVi vector<VVi>
#define Vm vector<mint>
#define Vs vector<string>
#define Vd vector<double>
#define Vc vector<char>
#define Pii pair<int,int>
#define Pdd pair<double,double>
#define VPii vector<Pii>
#define Tiii tuple<int,int,int>
#define VTiii vector<Tiii>
#define PQi priority_queue<int>
#define PQir priority_queue<int,vector<int>,greater<int>>
#define pb push_back
#define mp make_pair
#define mt make_tuple
#define itos to_string
#define stoi stoll
#define FI first
#define SE second
#define cYES cout<<"YES"<<endl
#define cNO cout<<"NO"<<endl
#define cYes cout<<"Yes"<<endl
#define cNo cout<<"No"<<endl
#define cyes cout<<"yes"<<endl
#define cno cout<<"no"<<endl
#define sortr(v) sort(v,greater<>())
#define rep(i,a,b) for(int i=a;i<b;i++)
#define repeq(i,a,b) for(int i=a;i<=b;i++)
#define repreq(i,a,b) for(int i=a;i>=b;i--)
#define dem(a,b) ((a+b-1)/(b))
#define INF 3000000000000000000 // 3.0*10^18
#define MAX LLONG_MAX
#define PI acos(-1.0L)
//int MOD = 998244353; // case
const int MOD = 1000000007; // 10^9 + 7
const double EPS = 1e-4;

using namespace std;

struct mint{int x;mint(int x=0):x((x%MOD+MOD)%MOD){}
mint operator-()const{return mint(-x);}
mint& operator+=(const mint a){if((x+=a.x)>=MOD)x-=MOD;return*this;}
mint& operator-=(const mint a){if((x+=MOD-a.x)>=MOD)x-=MOD;return*this;}
mint& operator*=(const mint a){(x*=a.x)%=MOD;return*this;}
mint operator+(const mint a)const{return mint(*this)+=a;}
mint operator-(const mint a)const{return mint(*this)-=a;}
mint operator*(const mint a)const{return mint(*this)*=a;}
mint pow(int t)const{if(!t)return 1;mint a=pow(t>>1);a*=a;if(t&1)a*=*this;return a;}
mint inv()const{return pow(MOD-2);}
mint& operator/=(const mint a){return*this*=a.inv();}
mint operator/(const mint a)const{return mint(*this)/=a;}};
istream& operator>>(istream& is, const mint& a) {return is >> a.x;}
ostream& operator<<(ostream& os, const mint& a) {return os << a.x;}

/* debug */
template <typename T> // vector
ostream& operator<<(ostream& os,const vector<T> &V){int N=V.size();
if(N==0){os<<'.';return os;}rep(i,0,N-1){os<<V[i]<<' ';}os<<V[N-1];return os;}
template <typename T> // vector vector
ostream& operator<<(ostream& os,const vector<vector<T>> &V){
int N=V.size();rep(i,0,N-1)cout<<V[i]<<endl;cout<<V[N-1];return os;}
template <typename T,typename S> // pair
ostream& operator<<(ostream& os, pair<T,S> const&P){os<<P.FI<<' '<<P.SE;return os;}
template <typename T> // set
ostream& operator<<(ostream& os,set<T> &S){auto it=S.begin();while(it!=S.end()){
os<<*it;if(next(it,1)!=S.end())os<<' ';it++;};return os;}
template <typename T> // deque
ostream& operator<<(ostream& os, deque<T> &q){for(auto it=q.begin();it<q.end();it++){
os<<*it;if(it+1!=q.end())os<<" ";}return os;}

/* useful */
template<typename T>void Vin(vector<T> &v){int n=v.size();rep(i,0,n)cin>>v[i];}
int gcd(int a,int b){return b?gcd(b,a%b):a;}
int lcm(int a,int b){return a/gcd(a,b)*b;}
int mypow(int x, int n, int m){
if(n==0)return 1;if(n%2==0)return mypow(x*x%m,n/2,m);else return x*mypow(x,n-1,m)%m;}
int scomb(int n, int r){if(r<0||r>n)return 0;if((n-r)<r)r=n-r; // nCr
int a=1;for(int i=n;i>n-r;--i){a=a*i;}for(int i=1;i<r+1;++i){a=a/i;}return a;}
Vi vis(Vi &v){Vi S(v.size()+1);rep(i,1,S.size())S[i]+=v[i-1]+S[i-1];return S;}
int digitsum(int n){int ret=0; while(n>0){ret+=n%10;n/=10;}return ret;}
int digit(int k,int i){string s = itos(k);return s[s.size()-i]-'0';} // i桁目の数字
template<typename T>void press(T &v){v.erase(unique(ALL(v)),v.end());} // 圧縮
Vi zip(Vi b){int Z=b.size(); // 座標圧縮
Pii p[Z+10];int a=b.size();Vi l(a);for(int i=0;i<a;i++)
p[i]=mp(b[i],i);sort(p,p+a);int w=0;for(int i=0;i<a;i++)
{if(i&&p[i].first!=p[i-1].first)w++;l[p[i].second]=w;}return l;}
Vi nibe2V(){Vi a(60);int q = 1;rep(i,0,60){a[i]=q;q*=2;}return a;}
//Vi nibe = nibe2V(); // 2^n
int modiv(int a,int b){return a*mypow(b,MOD-2,MOD)%MOD;} // a÷b(%MOD)
int SMALLER(Vi &a,int x){return lower_bound(a.begin(),a.end(),x)-a.begin();}
int orSMALLER(Vi &a,int x){return upper_bound(a.begin(),a.end(),x)-a.begin();}
int BIGGER(Vi &a,int x){return a.size()-orSMALLER(a,x);}
int orBIGGER(Vi &a,int x){return a.size()-SMALLER(a,x);}
int COUNT(Vi &a,int x) {return upper_bound(ALL(a),x)-lower_bound(ALL(a),x);}
int maxind(Vi &a){return max_element(ALL(a))-a.begin();}
int minind(Vi &a){return min_element(ALL(a))-a.begin();}
Vi stpowV(){Vi a(1000005);a[0]=1;repeq(i,1,1000004)a[i]=a[i-1]*i%MOD;return a;}
//Vi stpow = stpowV(); // 階乗配列(%MOD)

/****************************** START ******************************/

struct graph_p {
  
  int N;
  vector<vector<pair<int,double>>> gr;
  vector<double> dist;
  vector<int> prever;
  
  graph_p(int n){
    init(n);
  }
  
  void init(int n){
    N = n;
    gr.resize(n);
    dist.resize(n,INF);
  }
  
  void add_edge(int a,int b,double c){
    gr[a].pb(mp(b,c));
  }
  
  void dijkstra(int s){
    int n = gr.size();
    dist = vector<double>(n);
    prever = vector<int>(n,-1);
    rep(i,0,n) dist[i]=INF;
    dist[s] = 0;
    
    priority_queue<tuple<double,int,int>,vector<tuple<double,int,int>>,
    greater<tuple<double,int,int>>> q;
    q.push(make_tuple(0,s,-1));
    while(!q.empty()){
      double nowdist,now,past;
      tie(nowdist,now,past)=q.top();
      q.pop();
      if(nowdist>dist[now]) continue;
      dist[now]=nowdist;
      rep(i,0,gr[now].size()){
        double next=gr[now][i].first,cost=gr[now][i].second;
        if(next!=past && nowdist+cost<dist[next]){
          prever[next] = now; // テスト
          q.push(make_tuple(nowdist+cost,next,now));
          dist[next]=nowdist+cost;
        }
      }
    }
    return;
  }

  vector<int> get_path(int t){ //頂点tへの最短路
    if(dist[t] >= INF) return {-1};
    vector<int> path;
    for(;t!=-1;t=prever[t]){
      path.push_back(t);
    }
    reverse(path.begin(), path.end());
    return path;
  }
  
};

double dd(Pdd A,Pdd B){ // 2点間の距離
   return sqrt((A.FI-B.FI)*(A.FI-B.FI)+(A.SE-B.SE)*(A.SE-B.SE));
 }

void sol(){
  int a,b,c,d;cin >> a >> b >> c >> d;
  int n;cin >> n;
  n += 2;
  Vi x(n),y(n),r(n);
  rep(i,0,n-2){
    cin >> x[i+1] >> y[i+1] >> r[i+1];
  }
  x[0] = a;
  y[0] = b;
  x[n-1] = c;
  y[n-1] = d;
  graph_p gr(n);
  
  rep(i,0,n)rep(j,0,n){
    if(i==j) continue;
    double now = dd(mp(x[i],y[i]),mp(x[j],y[j]));
    //cout << now << endl;
    gr.add_edge(i,j,max(0.0,now-r[i]-r[j]));
  }
  gr.dijkstra(0);
  cout << gr.dist[n-1] << endl;
}

signed main() {
  cin.tie(0);cout.tie(0);ios::sync_with_stdio(false);cout<<fixed<<setprecision(12);
  int q = 1;
  //cin >> q;
  rep(i,0,q) sol();
  return 0;
}

Measured memory_bytes: 25652