#include <cstdio>
#include <algorithm>
#include <stack>
#include <queue>
#include <deque>
#include <vector>
#include <string>
#include <string.h>
#include <cstdlib>
#include <ctime>
#include <cmath>
#include <map>
#include <set>
#include <iostream>
#include <sstream>
#include <numeric>
#include <cctype>
#include <bitset>
#include <cassert>
#define fi first
#define se second
#define rep(i,n) for(int i = 0; i < (n); ++i)
#define rrep(i,n) for(int i = 1; i <= (n); ++i)
#define drep(i,n) for(int i = (n)-1; i >= 0; --i)
#define gep(i,g,j) for(int i = g.head[j]; i != -1; i = g.e[i].next)
#define each(it,c) for(__typeof((c).begin()) it=(c).begin();it!=(c).end();it++)
#define rng(a) a.begin(),a.end()
#define maxs(x,y) x = max(x,y)
#define mins(x,y) x = min(x,y)
#define pb push_back
#define sz(x) (int)(x).size()
#define pcnt __builtin_popcount
#define uni(x) x.erase(unique(rng(x)),x.end())
#define snuke srand((unsigned)clock()+(unsigned)time(NULL));
#define df(x) int x = in()
#define dame { puts("-1"); return 0;}
#define show(x) cout<<#x<<" = "<<x<<endl;
#define PQ(T) priority_queue<T,vector<T>,greater<T> >
using namespace std;
typedef long long int ll;
typedef pair<int,int> P;
typedef pair<double,P> DP;
typedef vector<int> vi;
typedef vector<vi> vvi;
typedef vector<ll> vl;
typedef vector<P> vp;
inline int in() { int x; scanf("%d",&x); return x;}
inline void priv(vi a) { rep(i,sz(a)) printf("%d%c",a[i],i==sz(a)-1?'\n':' ');}
template<typename T>istream& operator>>(istream&i,vector<T>&v)
{rep(j,sz(v))i>>v[j];return i;}
template<typename T>string join(vector<T>&v)
{stringstream s;rep(i,sz(v))s<<' '<<v[i];return s.str().substr(1);}
template<typename T>ostream& operator<<(ostream&o,vector<T>&v)
{if(sz(v))o<<join(v);return o;}
template<typename T1,typename T2>istream& operator>>(istream&i,pair<T1,T2>&v)
{return i>>v.fi>>v.se;}
template<typename T1,typename T2>ostream& operator<<(ostream&o,pair<T1,T2>&v)
{return o<<v.fi<<","<<v.se;}
const int MX = 15, INF = 1001001001;
const ll LINF = 1e18;
const double eps = 1e-10;
double yosupot(double a, double b) { return sqrt(a * a + b * b);}

// Union find
struct uf {
  vi d;
  uf(){}
  uf(int mx):d(mx,-1){}
  int root(int x) {
    if(d[x] < 0) return x;
    return d[x] = root(d[x]);
  }
  bool unite(int x, int y) {
    x = root(x); y = root(y);
    if(x == y) return false;
    if(d[x] > d[y]) swap(x,y);
    d[x] += d[y]; d[y] = x;
    return true;
  }
  int size(int x) { return -d[root(x)];}
};
//

double d[1<<15];
double dp[1<<15];

int main() {
  int n;
  scanf("%d",&n);
  vi x(n), y(n), a(n);
  rep(i,n) scanf("%d%d%d",&x[i],&y[i],&a[i]);
  rep(i,1<<n) {
    if (!i) continue;
    vector<DP> es;
    rep(j,n) if (i>>j&1) {
      rep(k,n) if (i>>k&1) {
        es.pb(DP(yosupot(x[j]-x[k],y[j]-y[k]),P(j,k)));
      }
    }
    uf t(n);
    sort(rng(es));
    double now = 0;
    rep(j,n) if (i>>j&1) now += a[j];
    for (auto e : es) {
      if (t.unite(e.se.fi,e.se.se)) now -= e.fi;
    }
    now /= pcnt(i);
    d[i] = now;
  }
  dp[0] = 1e10;
  rep(i,1<<n) {
    int ii = ((1<<n)-1)^i;
    for (int j = ii; j; j = (j-1)&ii) {
      maxs(dp[i^j], min(dp[i],d[j]));
    }
  }
  printf("%.10f\n",dp[(1<<n)-1]);
  return 0;
}































Measured memory_bytes: 768