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

//using Graph = vector<vector<edge>>;
using dou =long double;
string yes="yes";
string Yes="Yes";
string YES="YES";
string no="no";
string No="No";
string NO="NO";

template<class T> inline bool chmax(T& a, T b) { if (a < b) { a = b; return true; } return false; }
template<class T> inline bool chmin(T& a, T b) { if (a > b) { a = b; return true; } return false; }
#define rep(i, n)         for(int i = 0; i < (int)(n); i++)
#define brep(n)           for(int bit=0;bit<(1<<n);bit++)
#define erep(i,container) for (auto i : container)
#define irep(i, n)        for(int i = n-1; i >= (int)0; i--)
#define rrep(i,m,n) for(ll i = m; i < (ll)(n); i++)
#define reprep(i,j,h,w) rep(i,h)rep(j,w)
#define all(x) (x).begin(),(x).end()
#define VEC(type,name,n) std::vector<type> name(n);rep(i,n)std::cin >> name[i];
#define pb push_back
#define pf push_front
#define query int qq;std::cin >> qq;rep(qqq,qq)
#define lb lower_bound
#define ub upper_bound
#define fi first
#define se second
#define itn int
#define mp make_pair
#define sum(a) accumulate(all(a),0ll)
#define keta fixed<<setprecision
#define vvector(name,typ,m,n,a)vector<vector<typ> > name(m,vector<typ> (n,a))
#define vvvector(name,t,l,m,n,a) vector<vector<vector<t> > > name(l, vector<vector<t> >(m, vector<t>(n,a)));
#define vvvvector(name,t,k,l,m,n,a) vector<vector<vector<vector<t> > > > name(k,vector<vector<vector<t> > >(l, vector<vector<t> >(m, vector<t>(n,a)) ));
#define case std::cout <<"Case #" <<qqq+1<<": "
#define RES(a,i,j) a.resize(i);rep(ii,i)a[ii].resize(j); 
#define as assign
#define ffor for(;;)
#define ppri(a,b) std::cout << a<<" "<<b << std::endl
#define pppri(a,b,c) std::cout << a<<" "<<b <<" "<< c<<std::endl
#define aall(x,n) (x).begin(),(x).begin()+(n)
#define ssum(a) accumulate(a,0ll) 
#define gre(n) greater<n>()

typedef long long ll;
typedef pair<dou,int> P;
typedef pair<ll,ll> PL;
//typedef long long T;
const int INF = 1000000000;
const ll INF64 = 922337203685477580ll;
const ll MOD = 1000000007ll;
const dou pi=3.141592653589793;
//メモ
//二次元配列のresizeのしかた

//vv.resize(n);
//for(size_t i=0; i<n; i++){
// vv[i].resize(n);
//}

//メモ
//負の辺を持つ最短経路問題では到達不可経路でも初期化値より小さくなりうるので注意しよう！
struct UnionFind {
    vector<int> par; // par[i]:iの親の番号　(例) par[3] = 2 : 3の親が2

    UnionFind(int N) : par(N) { //最初は全てが根であるとして初期化
        for(int i = 0; i < N; i++) par[i] = i;
    }

    int root(int x) { // データxが属する木の根を再帰で得る：root(x) = {xの木の根}
        if (par[x] == x) return x;
        return par[x] = root(par[x]);
    }

    void unite(int x, int y) { // xとyの木を併合
        int rx = root(x); //xの根をrx
        int ry = root(y); //yの根をry
        if (rx == ry) return; //xとyの根が同じ(=同じ木にある)時はそのまま
        par[rx] = ry; //xとyの根が同じでない(=同じ木にない)時：xの根rxをyの根ryにつける
    }

    bool same(int x, int y) { // 2つのデータx, yが属する木が同じならtrueを返す
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }
};
struct edge{
    int from,to;
    dou dist;
    edge(int from,int to,dou dist):
     from(from),to(to),dist(dist){}
};
struct Edge{
    int to;
    dou dist;
    Edge(int to,dou dist):
     to(to),dist(dist){}
};
std::vector<vector<Edge>> ki;
std::vector<edge> g;
std::vector<int> dum;
dou ans;
void Kruscal(int v,int e){
    ans=0;
    UnionFind u(v);
    priority_queue<P,std::vector<P>,greater<P>> q;
    rep(i,e){
        q.push(mp(g[i].dist,i));
    }
    rep(i,e){
        int p=q.top().se;
        if(!u.same(g[p].from,g[p].to)){
            u.unite(g[p].from,g[p].to);
            ki[g[p].from].pb(Edge(g[p].to,g[p].dist));
            ki[g[p].to].pb(Edge(g[p].from,g[p].dist));
            dum.pb(g[p].dist);
            ans+=g[p].dist;
        }
        q.pop();
    }
}
double ww(double a,double b){
    return (a-b)*(a-b);
}
double www(double a,double b,double c,double d,double e,double f,double dd,double ddd){
    return max(0.0,sqrt(ww(a,d)+ww(b,e)+ww(c,f))-(dd+ddd));
}
int main(){
    ffor{
        itn n;
        std::cin >> n;
        if(n==0)break;
        ki.resize(n);
        std::vector<dou> x(n),y(n),z(n),d(n);
        rep(i,n)std::cin >> x[i]>>y[i]>>z[i]>>d[i];
        reprep(i,j,n,n){
            g.pb(edge(i,j,www(x[i],y[i],z[i],x[j],y[j],z[j],d[i],d[j])));
        }
        Kruscal(n,g.size());
        std::cout <<keta(3)<< ans << std::endl;
        g.clear();
    }
}


Measured memory_bytes: 4224