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

#define int long long
#define all(x) (x).begin(), (x).end()
#define rall(x) (x).rbegin(), (x).rend()
#define rep(i, n) for (int i = 0; i < n; ++i)
#define REP(i, n) for (int i = 0; i < n; ++i)
#define range(i,a,b) ((a)<=(i) && (i)<(b))
#define debug(x) cout << #x << " = " << (x) << endl;
#define fs first
#define sc second
#define pb push_back
#define eb emplace_back
#define SP << " " <<

typedef long long ll;
typedef pair<int, double> P;
typedef tuple<int, int, int> T;
typedef vector<int> vec;
typedef vector<P> pvec;
typedef vector<vector<int>> vvec;
typedef vector<vector<P>> pvvec;
typedef priority_queue<int> PQI;
typedef priority_queue<P> PQP;
typedef priority_queue<int,vector<int>,greater<int>> PQIG;
typedef priority_queue<P,vector<P>,greater<P>> PQPG;

const vector<int> DX = {0, -1, 0, 1, 1, 1, -1, -1};
const vector<int> DY = {1, 0, -1, 0, 1, -1, 1, -1};
constexpr int MOD = (1000000007);
// const int MOD = (998244353);
// const int INF = (1 << 30); // 1073741824
const ll INF = (1LL << 60); // 1152921504606846976
const double PI = (3.141592653589794);
const double EPS = (0.0000000001); // 10^(-10)

template<class T> inline bool chmin(T& a, T b) {if (a > b) {a = b; return 1;} return 0;}
template<class T> inline bool chmax(T& a, T b) {if (a < b) {a = b; return 1;} return 0;}
template<class T> inline T ceil(T a, T b) {return T((a + b - 1) / b);}
template<class T> inline T round(T a, T b) {return T(a / b);}
template< typename T1, typename T2 > istream &operator>>(istream &is, pair< T1, T2 > &p) { is >> p.first >> p.second; return is; }
template <class T> inline void out(T &a) { bool flag=true; for(auto&x:a){if(flag) {flag=false;} else{ cout << ' '; } cout<<x; } cout << endl; }



//----------------------------------------------------------------
int nmax=200000; // 2*(10^5)



typedef vector<vector<P>> Graph;
vector<double> dijkstra(int s, Graph &G){
  priority_queue<P,vector<P>,greater<P>> que;
  int n = G.size();
  vector<double> dist(n);
  dist.assign(n,INF);
  dist[s] = 0;
  que.push(P(0,s));

  while(!que.empty()){
    P p = que.top();
    que.pop();
    int v = p.sc;
    REP(i,G[v].size()){
      if(dist[G[v][i].fs] > dist[v]+G[v][i].sc){
        dist[G[v][i].fs] = dist[v]+G[v][i].sc;
        que.push(P(dist[G[v][i].fs],G[v][i].fs));
      }
    }
  }
  return dist;
}

void solve4ts()
{
    
    int a,b,c,d,n;
    cin>>a>>b>>c>>d>>n;

    vector<T> x;
    x.eb(a,b,0);
    x.eb(c,d,0);

    rep(i,n){
        cin>>a>>b>>c;
        x.eb(a,b,c);
    }

    Graph G(1100);
    rep(i,n+2){
        rep(j,n+2){
            if(i<j){
                tie(a,b,c)=x[i];
                int e,f;
                tie(d,e,f)=x[j];
                double dist=sqrt((a-d)*(a-d)+(b-e)*(b-e));
                dist-=c+f;
                if(dist<=0) dist=0;
                G[i].eb(j,dist);
                G[j].eb(i,dist);
            }
        }
    }

    vector<double> ans=dijkstra(0,G);
    cout<<ans[1]<<endl;
}
//-----------------------------------------------------------------

signed main(){ ios::sync_with_stdio(false); cin.tie(0); cout << fixed << setprecision(15);
    int repeat = 1;
    // cin >> repeat;
    while(repeat--) solve4ts();
}

Measured memory_bytes: 22000