#pragma GCC optimize("Ofast")
#pragma GCC target("sse,sse2,sse3,ssse3,sse4,popcnt,abm,mmx,avx,tune=native")
#include<iostream>
#include<fstream>
#include<iomanip>
#include<cstdio>
#include<string>
#include<cstring>
#include<climits>
#include<algorithm>
#include<vector>
#include<cmath>
#include<map>
#include<set>
#include<stack>
#include<queue>
#include<deque>
#include<tuple>
#include<list>
#include<unordered_map>
#include<unordered_set>
#include<random>
#include<functional>
#define ll long long
#define ull unsigned long long
#define pii pair<int,int>
#define pp pair<pair<ll, ll>,pair<ll, ll>>
#define pll pair<ll,ll>
#define pdd pair<double,double>
#define vii vector<int>
#define vll vector<ll>
#define mat vector<vector<ll>>
#define lb lower_bound
#define pb push_back
#define mp make_pair
#define fi first
#define sc second
#define rep(i,n) for(ll i=0;i<n;i++)
#define rep2(i,a,b) for(ll i=a;i<b;i++)
#define repr(i,n) for(ll i=n-1;i>=0;i--)
#define all(x) x.begin(),x.end()
#define LB(v,x) (lower_bound(v.begin(),v.end(),x)-v.begin())
#define UB(v,x) (upper_bound(v.begin(),v.end(),x)-v.begin())
#define ERASE(v) v.erase(unique(v.begin(),v.end()),v.end())
// #define int ll
using namespace std;
const ll INF = (1 << 30 ) - 1;
const ll LLINF = (1LL << 60LL);
const ll MOD = 1000000007;
const ll mod = 998244353;
const ll MAX = 1100000;
const double pi = acos(-1);
const double eps = 1e-10;
ll dx[4] ={1,0,-1,0} , dy[4] ={0,1,0,-1};


static const int COUNTER_CLOCKWISE = 1;
static const int CLOCKWISE = -1;
static const int ONLINE_BACK = 2;
static const int ONLINE_FRONT = -2;
static const int ON_SEGMENT = 0;


template<class T>
bool equals(T a,T b){ return fabs((a)-(b)) < eps; }

struct Point{
    double x, y;
    Point(){}
    Point(double x, double y) : x(x), y(y){}
    Point operator + (Point p) { return Point(x+p.x, y+p.y); }
    Point operator - (Point p) { return Point(x-p.x, y-p.y); }
    Point operator * (double a) { return Point(x*a, y*a); }
    Point operator / (double a) { return Point(x/a, y/a); }
    double norm() {return x*x+y*y;}
    double abs() {return sqrt(norm());}

    bool operator < (const Point &p) const {
        return x!=p.x ? x<p.x : y<p.y;
    }
    bool operator > (const Point &p) const {
        return x!=p.x ? x>p.x : y>p.y;
    }
    bool operator == (const Point &p) const {
        return fabs(x-p.x) < eps && fabs(y-p.y) < eps;
    }
};

istream &operator >> (istream &is, Point &p){
    is>>p.x>>p.y;
    return is;
}
ostream &operator << (ostream &os, Point p){
    os<<p.x<<" "<<p.y;
    return os;
}

bool sort_x(Point a, Point b){ return !equals(a.x,b.x)?a.x<b.x:a.y<b.y; }
bool sort_y(Point a, Point b){ return !equals(a.y,b.y)?a.y<b.y:a.x<b.x; }

typedef Point Vector;
typedef vector<Point> Polygon;
double norm(Vector a) { return a.x*a.x+a.y*a.y; }
double abs(Vector a) { return sqrt(norm(a)); }
double dot(Vector a, Vector b) { return a.x*b.x+a.y*b.y; }
double cross(Vector a, Vector b) { return a.x*b.y-a.y*b.x; }

struct Segment {
    Point p1, p2;
    Segment(){}
    Segment(Point p1, Point p2):p1(p1),p2(p2){}
};
typedef Segment Line;

struct Circle{
    Point c;
    double r;
    Circle(){}
    Circle(Point c, double r) : c(c),r(r) {}
};

int ccw(Point p0, Point p1, Point p2){
    Vector a=p1-p0;
    Vector b=p2-p0;
    if(cross(a,b)>eps) return COUNTER_CLOCKWISE;
    if(cross(a,b)< -eps) return CLOCKWISE;
    if(dot(a,b)< -eps) return ONLINE_BACK;
    if(a.norm() < b.norm()) return ONLINE_FRONT;
    return ON_SEGMENT;
}

bool intersect(Point p1, Point p2, Point  p3, Point p4){
    return (ccw(p1,p2,p3)*ccw(p1,p2,p4)<=0&&ccw(p3,p4,p1)*ccw(p3,p4,p2)<=0);
}
bool intersect(Segment s1, Segment s2){
    return intersect(s1.p1, s1.p2, s2.p1, s2.p2);
}

bool isOrthogonal(Vector a, Vector b){
    return equals(dot(a,b), 0.0);
}
bool isOrthogonal(Point a1, Point a2, Point b1, Point b2){
    return isOrthogonal(a1-a2, b1-b2);
}
bool isOrthogonal(Segment s1, Segment s2){
    return equals(dot(s1.p2-s1.p1, s2.p2-s2.p1),0.0);
}

bool isParallel(Vector a, Vector b){
    return equals(cross(a,b), 0.0);
}
bool isParallel(Point a1, Point a2, Point b1, Point b2){
    return isParallel(a1-a2, b1-b2);
}
bool isParallel(Segment s1, Segment s2){
    return equals(cross(s1.p2-s1.p1, s2.p2-s2.p1),0.0);
}

Point project(Segment s, Point p){
    Vector base=s.p2-s.p1;
    double r=dot(p-s.p1,base)/norm(base);
    return s.p1+base*r;
}
Point reflect(Segment s,Point p){
    return p+(project(s,p)-p)*2.0;
}

double getDistance(Point a, Point b){
    return abs(a-b);
}
double getDistanceLP(Line l, Point p){
    return abs(cross(l.p2-l.p1, p-l.p1))/abs(l.p2-l.p1);
}
double getDistanceSP(Segment s, Point p){
    if(dot(s.p2-s.p1,p-s.p1) < 0.0) return abs(p-s.p1);
    if(dot(s.p1-s.p2,p-s.p2) < 0.0) return abs(p-s.p2);
    return getDistanceLP(s,p);
}
double getDistanceSS(Segment s1, Segment s2){
    if(intersect(s1,s2)) return 0.0;
    return min( min(getDistanceSP(s1,s2.p1),getDistanceSP(s1,s2.p2)),
                min(getDistanceSP(s2,s1.p1),getDistanceSP(s2,s1.p2)));
}

Point getCrossPoint(Segment s1, Segment s2){
    Vector base=s2.p2-s2.p1;
    double d1=abs(cross(base, s1.p1-s2.p1));
    double d2=abs(cross(base, s1.p2-s2.p1));
    double t=d1/(d1+d2);
    return s1.p1+(s1.p2-s1.p1)*t;
}

pair<Point, Point> getCrossPoints(Circle c, Line l){
    Vector pr=project(l,c.c);
    Vector e=(l.p2-l.p1)/abs(l.p2-l.p1);
    double base=sqrt(c.r*c.r-norm(pr-c.c));
    return make_pair(pr+e*base, pr-e*base);
}

bool isConvex(Polygon s){
    ll n=s.size();
    rep(i,n){
        if(ccw(s[(i+n-1)%n],s[i],s[(i+1)%n])==CLOCKWISE) return false;
    }
    return true;
}

double PolygonArea(Polygon s){
    double res=0.0;
    rep(i,s.size()){
        res+=cross(s[i],s[(i+1)%s.size()])/2.0;
    }
    return abs(res);
}


signed main(){
    cin.tie(0);
    ios::sync_with_stdio(false);
    cout << fixed << setprecision(15);
    ll n;
    double cost[1010][1010],r[1010];
    double x,y;
    Point p[1010];
    cin>>p[0];
    cin>>x>>y;
    cin>>n;
    p[n+1]=Point(x,y);
    r[0]=0.0,r[n+1]=0.0;
    rep2(i,1,n+1){
        cin>>p[i]>>r[i];
    }
    rep(i,n+2){
        rep(j,n+2){
            cost[i][j]=max(0.0,getDistance(p[i],p[j])-(r[i]+r[j]));
        }
    }
    double d[1010];
    bool used[1010];
    fill(d,d+n+2,LLINF);
    fill(used,used+n+2,false);
    d[0]=0.0;
    while(true){
        ll v=-1;
        rep(u,n+2){
            if(!used[u]&&(v==-1||d[u]<d[v])) v=u;
        }
        if(v==-1){
            break;
        }
        used[v]=true;
        rep(u,n+2){
            d[u]=min(d[u],d[v]+cost[v][u]);
        }
    }
    cout<<d[n+1]<<endl;
    /*
    rep(i,n+2){
        rep(j,n+2){
            cout<<i<<" "<<j<<" "<<cost[i][j]<<endl;
        }
    }
    */
    return 0;
}

Measured memory_bytes: 8320