#include<bits/stdc++.h>
using namespace std;


#define li          long long int
#define rep(i,to)   for(li i=0;i<((li)(to));i++)
#define repp(i,start,to)    for(li i=(li)(start);i<((li)(to));i++)
#define pb          push_back
#define sz(v)       ((li)(v).size())
#define bgn(v)      ((v).begin())
#define eend(v)     ((v).end())
#define allof(v)    (v).begin(), (v).end()
#define dodp(v,n)       memset(v,(li)n,sizeof(v))
#define bit(n)      (1ll<<(li)(n))
#define mp(a,b)     make_pair(a,b)
#define rin rep(i,n)
#define EPS 1e-12
#define ETOL 1e-8
#define MOD 998244353
typedef pair<li, li> PI;

#define INF bit(60)

#define DBGP 1


#define idp if(DBGP)
#define F first
#define S second
#define p2(a,b)     idp cout<<a<<"\t"<<b<<endl
#define p3(a,b,c)       idp cout<<a<<"\t"<<b<<"\t"<<c<<endl
#define p4(a,b,c,d)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<endl
#define p5(a,b,c,d,e)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<endl
#define p6(a,b,c,d,e,f)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<endl
#define p7(a,b,c,d,e,f,g)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<endl
#define p8(a,b,c,d,e,f,g,h)     idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<endl
#define p9(a,b,c,d,e,f,g,h,i)       idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<endl
#define p10(a,b,c,d,e,f,g,h,i,j)        idp cout<<a<<"\t"<<b<<"\t"<<c<<"\t"<<d<<"\t"<<e<<"\t"<<f<<"\t"<<g<<"\t"<<h<<"\t"<<i<<"\t"<<j<<endl
#define foreach(it,v)   for(__typeof((v).begin()) it=(v).begin(); it!=(v).end(); ++it)
#define p2p(x)      idp p2((x).F, (x).S)
#define dump(x,n)   idp{rep(i,n){cout<<x[i]<<" ";}puts("");}
#define dump2(x,n)  idp{rep(i,n){cout<<"["<<x[i].F<<" , "<<x[i].S<<"] ";}puts("");}
#define dumpi(x)    idp{foreach(it, x){cout<<(*it)<<" ";}puts("");}
#define dumpi2(x)   idp{foreach(it, x){cout<<"["<<(it)->F<<" , "<<(it)->S<<"] ";}puts("");}

#define read2d(a,w,h)   rep(i,h)rep(j,w)cin>>a[i][j]
#define dump2d(a,w,h)   rep(i,h){rep(j,w)cout<<a[i][j]<<" ";puts("");}

typedef pair<li, li> PI;

double cost[1010][1010];
li n;

PI b[1010];
li r[1010];

inline double distance(PI x, PI y) {
    return hypot(x.F - y.F, x.S - y.S);
}

inline double dijkstra(li from, li to) {
    priority_queue<pair<double, li>> pq;
    vector<double> distance(n + 2, INF);
    pq.push({0.0, from});
    while (!pq.empty()) {
        li now = pq.top().S;
        double now_cost = -pq.top().F;
        pq.pop();
        if (now_cost >= distance[now]) {
            continue;
        }
        distance[now] = now_cost;
        if (now == to) {
            return distance[now];
        }
        rep(i, n + 2) {
            if (i == now) {
                continue;
            }
            double next_cost = now_cost + cost[now][i];
            pq.push({ -next_cost, i});
        }
    }
    return -1;
}

int main() {
    PI from, to;
    cin >> from.F >> from.S >> to.F >> to.S;
    cin >> n;
    cost[n][n + 1] = cost[n + 1][n] = distance(from, to);

    rin{
        cin >> b[i].F >> b[i].S >> r[i];
        cost[n][i] = cost[i][n] = max(0.0, distance(from, b[i]) - r[i]);
        cost[n + 1][i] = cost[i][n + 1] = max(0.0, distance(to, b[i]) - r[i]);
    }
    rep(i, n) {
        rep(j, n) {
            cost[i][j] = max(0.0, distance(b[i], b[j]) - r[i] - r[j]);
        }
    }

    printf("%.12f\n", dijkstra(n, n + 1));

    return 0;
}

Measured memory_bytes: 26732