#include<stdio.h>
#include<cstring>
#include<cstdlib>
#include<cmath>
#include<iostream>
#include<algorithm>
#include<vector>
#include<map>
#include<set>
#include<queue>
#include<bitset>
#include<utility>
#include<functional>
#include<iomanip>
#include<sstream>
#include<ctime>
#include<cassert>
using namespace std;
#define y0 y0z
#define y1 y1z
#define yn ynz
#define j0 j0z
#define j1 j1z
#define jn jnz
#define tm tmz
#define buli(x) (__builtin_popcountll(x))
#define bur0(x) (__builtin_ctzll(x))
#define bul2(x) (63-__builtin_clzll(x))
#define mp make_pair
#define pb push_back
#define fi first
#define se second
#define fil(a,b) memset((a),(b),sizeof(a))
#define cl(a) fil(a,0)
#define siz(x) ((int)(x).size())
#define all(x) (x).begin(),(x).end()
#define foreach(it,a) for(__typeof((a).begin()) it=(a).begin();it!=(a).end();it++)
#define rep(i,a,b) for (int i=(a),_ed=(b);i<_ed;i++)
#define per(i,a,b) for (int i=(b)-1,_ed=(a);i>=_ed;i--)
#define forg(i,gu) for (int i=gu;~i;i=e[i].next)
#define pw(x) ((ll(1))<<(x))
#define upmo(a,b) (((a)=((a)+(b))%mo)<0?(a)+=mo:(a))
#define mmo(a,b) (((a)=1ll*(a)*(b)%mo)<0?(a)+=mo:(a))
void getre(){int x=0;printf("%d\n",1/x);}
void gettle(){int res=1;while(1)res<<=1;printf("%d\n",res);}
typedef pair<int,int> pii;
typedef vector<int> vi;
typedef vector<pii> vpii;
template<typename T,typename S>inline bool upmin(T&a,const S&b){return a>b?a=b,1:0;}
template<typename T,typename S>inline bool upmax(T&a,const S&b){return a<b?a=b,1:0;}
template<typename N,typename PN>inline N flo(N a,PN b){return a>=0?a/b:-((-a-1)/b)-1;}
template<typename N,typename PN>inline N cei(N a,PN b){return a>0?(a-1)/b+1:-(-a/b);}
template<typename N>N gcd(N a,N b){return b?gcd(b,a%b):a;}
template<typename N>inline int sgn(N a){return a>0?1:(a<0?-1:0);}
#if ( ( _WIN32 || __WIN32__ ) && __cplusplus < 201103L)
#define lld "%I64d"
#else
#define lld "%lld"
#endif
inline void gn(long long&x){
	int sg=1;char c;while(((c=getchar())<'0'||c>'9')&&c!='-');c=='-'?(sg=-1,x=0):(x=c-'0');
	while((c=getchar())>='0'&&c<='9')x=x*10+c-'0';x*=sg;
}
inline void gn(int&x){long long t;gn(t);x=t;}
inline void gn(unsigned long long&x){long long t;gn(t);x=t;}
inline void gn(double&x){double t;scanf("%lf",&t);x=t;}
inline void gn(long double&x){double t;scanf("%lf",&t);x=t;}
inline void gs(char *s){scanf("%s",s);}
inline void gc(char &c){while((c=getchar())>126 || c<33);}
inline void pc(char c){putchar(c);}
#ifdef JCVB
#define debug(...) fprintf(stderr, __VA_ARGS__)
#else
#define debug(...)
#endif
typedef long long ll;
typedef double db;
inline ll sqr(ll a){return a*a;}
inline db sqrf(db a){return a*a;}
const int inf=0x3f3f3f3f;
const db pi=3.14159265358979323846264338327950288L;
const db eps=1e-6;
//const int mo=0;
//int qp(int a,ll b){int n=1;do{if(b&1)n=1ll*n*a%mo;a=1ll*a*a%mo;}while(b>>=1);return n;}

int n;

struct pkt{
	int x,y;
	void read(){gn(x);gn(y);}
	ll dissq(){return 1ll*x*x+1ll*y*y;}
	friend pkt operator+(const pkt&a,const pkt&b){return (pkt){a.x+b.x,a.y+b.y};}
	friend pkt operator-(const pkt&a,const pkt&b){return (pkt){a.x-b.x,a.y-b.y};}
	friend pkt operator-(const pkt&a){return (pkt){-a.x,-a.y};}
	friend ll dot(const pkt&a,const pkt&b){return 1ll*a.x*b.x+1ll*a.y*b.y;}
	friend ll cro(const pkt&a,const pkt&b){return 1ll*a.x*b.y-1ll*a.y*b.x;}
	friend bool operator<(const pkt&a,const pkt&b){return a.y==b.y?a.x<b.x:a.y<b.y;}
	/*friend bool operator<(const pkt&a,const pkt&b){
		int aa=a.y>0 || a.y==0&& a.x>0;
		int bb=b.y>0 || b.y==0&& b.x>0;
		if(aa!=bb)return aa<bb;
		else return cro(a,b)>0;
	}*/
}p[15];


db mst[1<<15];

int fa[15];
int gf(int x){
	return x==fa[x]?x:fa[x]=gf(fa[x]);
}
bool un(int u,int v){
	u=gf(u);v=gf(v);
	if(u!=v){
		fa[u]=v;
		return 1;
	}
	return 0;
}
struct edg{
	int u,v;
	db x;
}ee[1111];
int cmp(const edg&a,const edg&b){
	return a.x<b.x;
}
int etot;

db gao(int b){
	etot=0;
	rep(i,0,n)fa[i]=i;
	rep(i,0,n)if(pw(i)&b)rep(j,i+1,n)if(pw(j)&b){
		ee[++etot]=(edg){i,j,sqrt((p[i]-p[j]).dissq())};
	}
	sort(ee+1,ee+1+etot,cmp);
	db su=0.0;
	rep(i,1,etot+1){
		if(un(ee[i].u,ee[i].v))su+=ee[i].x;
	}
	return su;
}
db ini[15];

db f[1<<15];
int main()
{
#ifdef JCVB
	//freopen("1.in","r",stdin);
	//freopen("1.out","w",stdout);
	int _time_jc=clock();
#endif
	gn(n);
	rep(i,0,n){
		p[i].read();
		gn(ini[i]);
	}
	
	rep(b,1,pw(n)){
		mst[b]=gao(b);
	}
	rep(b,1,pw(n)){
		db mia=1e18;
		db su=0.0;
		int cnt=0;
		rep(i,0,n)if(pw(i)&b){
			upmin(mia,ini[i]);
			su+=ini[i];
			cnt++;
		}
		f[b]=mia;

		su-=mst[b];
		upmax(su,0.0);
		su/=cnt;
		upmax(f[b],su);
	}

	f[0]=0.0;
	rep(b,1,pw(n)){
		for (int x=b;x;x=(x-1)&b){
			upmax(f[b],min(f[x],f[b^x]));
		}
	}
	printf("%.10lf\n",f[pw(n)-1]);


#ifdef JCVB
	debug("time: %d\n",int(clock()-_time_jc));
#endif
	return 0;
}




Measured memory_bytes: 768