#include <bits/stdc++.h>
typedef long long ll;
const int INF = 1e9;
const int MOD = 1e9+7;
const ll LINF = 1e18;
using namespace std;
 
#define dump(x)  cout << #x << " = " << (x) << endl;
#define YES(n) cout << ((n) ? "YES" : "NO"  ) << endl
#define Yes(n) cout << ((n) ? "Yes" : "No"  ) << endl
#define POSSIBLE(n) cout << ((n) ? "POSSIBLE" : "IMPOSSIBLE"  ) << endl
#define Possible(n) cout << ((n) ? "Possible" : "Impossible"  ) << endl
#define possible(n) cout << ((n) ? "possible" : "impossible"  ) << endl
 
#define SANKOU(n,a,b) cout << ((n) ? (#a) : (#b) ) << endl
 
#define FOR(i,a,b) for(int i=(a);i<(b);++i)
#define REP(i,n) for(int i=0;i<(n);++i)
#define REPR(i,n) for(int i=n;i>=0;i--)
 
#define FOREACH(x,a) for(auto& (x) : (a) )
 
#define WFA(d,v) REP(k,v)REP(i,v)REP(j,v)d[i][j]=min(d[i][j],d[i][k]+d[k][j])
 
#define SCOUT(x) cout<<(x)<<" "
#define ENDL cout<<endl
 
#define VECCIN(x) for(auto&youso_: (x) )cin>>youso_
#define VECIN2(x,y) REP(i,x.size())cin>>x[i]>>y[i]
#define VECCOUT(x) if(1){for(auto tt=x.begin();tt!=x.end();tt++){if(tt!=x.begin())cout<<" ";cout<<(*tt);}cout<<endl;}
 
#define ALL(obj) (obj).begin(),(obj).end()
 
#define EXIST(n,x) (find(ALL(n),x)!=n.end())
#define UNIQUE(obj) sort(ALL( obj )); obj.erase(unique(ALL(obj)),obj.end())
#define EN(x) if(1){cout<<#x<<endl;return 0;}
#define COUT(x) cout<<(x)<<endl
void CINT(){}
template <class Head,class... Tail>
void CINT(Head&& head,Tail&&... tail){
    cin>>head;
    CINT(move(tail)...);
}
#define CIN(...) int __VA_ARGS__;CINT(__VA_ARGS__)
#define LCIN(...) ll __VA_ARGS__;CINT(__VA_ARGS__)
#define SCIN(...) string __VA_ARGS__;CINT(__VA_ARGS__)
 
template <class T = ll>
T IN(){T x;cin>>x;return (x);}
 
template <class Head>
void VT(Head head){}
template <class Head,class Seco,class... Tail>
void VT(Head&& head,Seco&& seco,Tail&&... tail){
    seco.resize(head);
    VT(head,move(tail)...);
}
void VT2(){}
template <class Head,class... Tail>
void VT2(Head&& head,Tail&&... tail){
    VECCIN(head);
    VT2(move(tail)...);
}
 
template <class Head>
void VT3(Head&& head){}
template <class Head,class Seco,class... Tail>
void VT3(Head&& head,Seco&& seco,Tail&&... tail){
    seco[head]=IN();
    VT3(head,move(tail)...);
}
 
#define VC1(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);VT2(__VA_ARGS__); //aaabbbccc
#define VC2(n,...) V __VA_ARGS__;VT(n,__VA_ARGS__);REP(i,n)VT3(i,__VA_ARGS__); //abcabcabc
 
//#include <boost/multiprecision/cpp_int.hpp>
//using namespace boost::multiprecision; // cpp_int
 
#define P pair<ll,ll>
#define V vector<ll>
#define M map<ll,ll>
#define S set<ll>
 
#define pb(a) push_back(a)
#define mp make_pair

class Dijkstra{
public:
    Dijkstra(vector<vector<pair<ll,double>>> ed,int firs,int pnum);
    void Solve();
    vector<double> range;// range[a]=b;
    vector<vector<pair<ll,double>>> edges;// [a][b]=c;
    // priority_queue<P,vector<P>,greater<P>> que;// queue=(range,point);
    priority_queue<pair<double,ll>,vector<pair<double,ll>>,greater<pair<double,ll>>> que;
};

Dijkstra::Dijkstra(vector<vector<pair<ll,double>>> ed,int firs,int pnum){
    edges=ed;
    vector<double> ttt(pnum,numeric_limits<double>::max());
    range=ttt;
    range[firs]=0;
    que.push(mp(0,firs));
}

void Dijkstra::Solve(){
    while(!que.empty()){
        pair<double,ll> top_=que.top();
        que.pop();
        FOREACH(x,edges[top_.second]){
            if(range[x.first] > range[top_.second] + x.second){
                range[x.first] = range[top_.second] + x.second;
                que.push(mp(range[x.first],x.first));
            }
        }
    }
}


int main(){
    CIN(x1,y1,x2,y2);
    CIN(n);VC2(n,x,y,r);
    x.pb(x1);x.pb(x2);
    y.pb(y1);y.pb(y2);
    r.pb(0);r.pb(0);
    vector<vector<pair<ll,double>>> edges(x.size());
    REP(i,x.size()){
        REP(j,x.size()){
            edges[i].pb(mp(j,max(0.0,
            sqrt(
                ((x[i]-x[j])*(x[i]-x[j]))
                +
                ((y[i]-y[j])*(y[i]-y[j]))
            )
            - r[i]-r[j]
            )));
            edges[j].pb(mp(i,max(0.0,
            sqrt(
                ((x[i]-x[j])*(x[i]-x[j]))
                +
                ((y[i]-y[j])*(y[i]-y[j]))
            )
            - r[i]-r[j]
            )));
        }
    }
    Dijkstra dijk(move(edges),n,x.size());
    dijk.Solve();
    //VECCOUT(dijk.range);
    printf("%.12lf\n",dijk.range[n+1]);

    return 0;
}

Measured memory_bytes: 66176