// 那就是希望。
// 即便需要取模，也是光明。

#include <algorithm>
#include <queue>
#include <math.h>
#include <stdio.h>
#include <vector>
typedef long long llt;
typedef unsigned uint;typedef unsigned long long ullt;
typedef bool bol;typedef char chr;typedef void voi;
typedef double dbl;
template<typename T>bol _max(T&a,T b){return(a<b)?a=b,true:false;}
template<typename T>bol _min(T&a,T b){return(b<a)?a=b,true:false;}
template<typename T>T lowbit(T n){return n&-n;}
template<typename T>T gcd(T a,T b){return b?gcd(b,a%b):a;}
template<typename T>T lcm(T a,T b){return(a!=0||b!=0)?a/gcd(a,b)*b:(T)0;}
template<typename T>T exgcd(T a,T b,T&x,T&y){if(b!=0){T ans=exgcd(b,a%b,y,x);y-=a/b*x;return ans;}else return y=0,x=1,a;}
template<typename T>T power(T base,T index,T mod)
{
    T ans=1%mod;
    while(index)
    {
        if(index&1)ans=ans*base%mod;
        base=base*base%mod,index>>=1;
    }
    return ans;
}
namespace Geo2D
{
    const dbl Pi=acosl(-1);
    const dbl eps=1e-9;
    struct Dbl
    {
        dbl v;
        Dbl():v(0){}
        Dbl(dbl v):v(v){}
        dbl&operator()(){return v;}
        voi read(){scanf("%lf",&v);}
        friend Dbl operator+(Dbl a){return a;}
        friend Dbl operator+(Dbl a,Dbl b){return a()+b();}
        friend Dbl operator-(Dbl a){return-a();}
        friend Dbl operator-(Dbl a,Dbl b){return a()-b();}
        friend Dbl operator*(Dbl a,Dbl b){return a()*b();}
        friend Dbl operator/(Dbl a,Dbl b){return a()/b();}
        friend bol operator<(Dbl a,Dbl b){return a()+eps<b();}
        friend bol operator>(Dbl a,Dbl b){return a()>b()+eps;}
        friend bol operator<=(Dbl a,Dbl b){return a()<b()+eps;}
        friend bol operator>=(Dbl a,Dbl b){return a()+eps>b();}
        friend bol operator==(Dbl a,Dbl b){return a()<b()+eps&&a()+eps>b();}
        friend bol operator!=(Dbl a,Dbl b){return a()>b()+eps||a()+eps<b();}
        Dbl _sin(){return sin(v);}
        Dbl _cos(){return cos(v);}
        Dbl _acos(){
            if(*this==1)return 0;
            if(*this==-1)return Pi;
            return acos(v);
        }
        Dbl _sqrt(){return sqrt(v);}
    };
    struct Vec
    {
        Dbl x,y;
        Vec():x(),y(){}
        Vec(Dbl x,Dbl y):x(x),y(y){}
        friend Vec operator+(Vec a,Vec b){return{a.x+b.x,a.y+b.y};}
        friend Vec operator-(Vec a,Vec b){return{a.x-b.x,a.y-b.y};}
        friend Vec operator*(Dbl a,Vec b){return{a*b.x,a*b.y};}
        friend Vec operator*(Vec a,Dbl b){return{a.x*b,a.y*b};}
        friend Dbl operator*(Vec a,Vec b){return a.x*b.x+a.y*b.y;}
        friend Dbl operator^(Vec a,Vec b){return a.x*b.y-a.y*b.x;}
        friend Vec operator/(Vec a,Dbl b){return{a.x/b,a.y/b};}
        friend bol operator==(Vec a,Vec b){return a.x==b.x&&a.y==b.y;}
        Vec&operator+=(Vec b){return*this=*this+b;}
        Vec&operator-=(Vec b){return*this=*this-b;}
        Dbl len_sqr(){return*this**this;}
        Dbl len(){return len_sqr()._sqrt();}
        friend Dbl dist_sqr(Vec a,Vec b){return(a-b).len_sqr();}
        friend Dbl dist(Vec a,Vec b){return(a-b).len();}
        voi read(){x.read(),y.read();}
        Vec rotate(Dbl c,Dbl s){return{c*x-s*y,s*x+c*y};}
        Vec rotate(Dbl angle){return rotate(angle._cos(),angle._sin());}
        int state()
        {
            if(x>0&&y==0)return 1;
            if(x>0&&y>0)return 2;
            if(x==0&&y>0)return 3;
            if(x<0&&y>0)return 4;
            if(x<0&&y==0)return 5;
            if(x<0&&y<0)return 6;
            if(x==0&&y<0)return 7;
            if(x>0&&y<0)return 8;
            return 0;
        }
    };
    bol cmp_atan2(Vec a,Vec b){
        if(a.state()!=b.state())return a.state()<b.state();
        return(a^b)>0;
    }
    typedef std::vector<Vec>Vecs;
    typedef Vec Point;
    typedef Vecs Points;
}
// Heaven and Earth... My guiding star...
// Akira Complex R.I.P.
using namespace Geo2D;
Point O[505],P[1000005];Dbl R[505],Dist[1000005];bol G[1000005];uint tp;
std::vector<uint>V[505];std::vector<std::pair<uint,Dbl> >Way[1000005];
int main()
{
#ifdef MYEE
    freopen("QAQ.in","r",stdin);
    freopen("QAQ.out","w",stdout);
#endif
    P[0].read(),P[1].read(),tp=2;
    uint n=0,m;scanf("%u",&m);while(m--)O[n].read(),R[n].read(),n+=R[n]!=0;
    auto check=[&](Point p,Point q)
    {
        if(p==q)return true;
        Vec f=q-p;Vec g=f/f.len_sqr();Dbl r;
        for(uint k=0;k<n;k++)if((r=g*(O[k]-p))>0&&r<1&&(p-O[k]+r*f).len()<R[k])return false;
        return true;
    };
    if(check(P[0],P[1]))Way[0].push_back({1,dist(P[0],P[1])}),Way[1].push_back({0,dist(P[0],P[1])});
    for(uint o=0;o<2;o++)for(uint i=0;i<n;i++)
    {
        Dbl d=dist(O[i],P[o]);Dbl c=R[i]/d;Dbl s=(1-c*c)._sqrt();Point p;
        p=O[i]+((P[o]-O[i])/d*R[i]).rotate(c,s);
        if(check(P[o],p))V[i].push_back(tp),
            Way[o].push_back({tp,dist(p,P[o])}),Way[tp].push_back({o,dist(p,P[o])}),P[tp++]=p;
        p=O[i]+((P[o]-O[i])/d*R[i]).rotate(c,-s);
        if(check(P[o],p))V[i].push_back(tp),
            Way[o].push_back({tp,dist(p,P[o])}),Way[tp].push_back({o,dist(p,P[o])}),P[tp++]=p;
    }
    for(uint i=0;i<n;i++)for(uint j=i+1;j<n;j++)
    {
        Dbl d=dist(O[i],O[j]),c,s;Point p,q;
        c=(R[i]+R[j])/d,s=(1-c*c)._sqrt();
        p=O[i]+((O[j]-O[i])/d*R[i]).rotate(c,s),q=O[j]+((O[i]-O[j])/d*R[j]).rotate(c,s);
        if(check(p,q))V[i].push_back(tp),V[j].push_back(tp+1),
            Way[tp].push_back({tp+1,dist(p,q)}),Way[tp+1].push_back({tp,dist(p,q)}),P[tp++]=p,P[tp++]=q;
        p=O[i]+((O[j]-O[i])/d*R[i]).rotate(c,-s),q=O[j]+((O[i]-O[j])/d*R[j]).rotate(c,-s);
        if(check(p,q))V[i].push_back(tp),V[j].push_back(tp+1),
            Way[tp].push_back({tp+1,dist(p,q)}),Way[tp+1].push_back({tp,dist(p,q)}),P[tp++]=p,P[tp++]=q;
        c=(R[i]-R[j])/d,s=(1-c*c)._sqrt();
        p=O[i]+((O[j]-O[i])/d*R[i]).rotate(c,s),q=O[j]+((O[i]-O[j])/d*R[j]).rotate(-c,-s);
        if(check(p,q))V[i].push_back(tp),V[j].push_back(tp+1),
            Way[tp].push_back({tp+1,dist(p,q)}),Way[tp+1].push_back({tp,dist(p,q)}),P[tp++]=p,P[tp++]=q;
        p=O[i]+((O[j]-O[i])/d*R[i]).rotate(c,-s),q=O[j]+((O[i]-O[j])/d*R[j]).rotate(-c,s);
        if(check(p,q))V[i].push_back(tp),V[j].push_back(tp+1),
            Way[tp].push_back({tp+1,dist(p,q)}),Way[tp+1].push_back({tp,dist(p,q)}),P[tp++]=p,P[tp++]=q;
    }
    for(uint i=0;i<n;i++)
    {
        std::sort(V[i].begin(),V[i].end(),[&](uint a,uint b){return cmp_atan2(P[a]-O[i],P[b]-O[i]);});
        for(uint j=0,a=V[i].back(),b;j<V[i].size();a=b,j++)
        {
            b=V[i][j];
            Dbl d=((P[a]-O[i])*(P[b]-O[i])/(R[i]*R[i]))._acos()*R[i];
            Way[a].push_back({b,d}),Way[b].push_back({a,d});
        }
    }
    for(uint i=1;i<tp;i++)Dist[i]=2e5;
    std::priority_queue<std::pair<Dbl,uint>,std::vector<std::pair<Dbl,uint> >,std::greater<std::pair<Dbl,uint> > >Q;
    Q.push({0,0});
    while(Q.size())
    {
        uint p=Q.top().second;Q.pop();if(G[p])continue;
        G[p]=1;for(auto s:Way[p])if(_min(Dist[s.first],Dist[p]+s.second))Q.push({Dist[s.first],s.first});
    }
    printf("%.1lf\n",Dist[1]());
    return 0;
}

// 那就是希望。
// 即便需要取模，也是光明。