``````#include<cstdio>
#include<cstring>
#include<algorithm>
#include<iostream>
#include<string>
#include<vector>
#include<stack>
#include<bitset>
#include<cstdlib>
#include<cmath>
#include<math.h>

#define LL long long
using namespace std;

LL x[1005], y[1005], z[1005];
LL mp[1005][1005];
double w[1005][1005];

int check(double mid, int n){

double dis[1005]={0};
bool vis[1005]={0};
double sum=0;
for(int i=1; i<=n; i++){
dis[i]=mp[1][i]-mid*w[1][i];//以dis[i]为参照，选取最小的n-1个
}
vis[1]=1;
int N=n-1;
while(N--){
double min_f=(1ll<<50);
int v=-1;
for(int j=1; j<=n; j++){
if(vis[j]==0&&dis[j]<min_f){
min_f=dis[j];
v=j;
}
}
sum+=min_f;
vis[v]=1;
for(int i=1; i<=n; i++){
if(vis[i]==0&&mp[v][i]-mid*w[v][i]<dis[i]){
dis[i]=mp[v][i]-mid*w[v][i];
}
}
}
return sum>=0;
}

int main(){

int n;
while(scanf("%d", &n), n){

for(int i=1; i<=n; i++){
scanf("%lld%lld%lld", &x[i], &y[i], &z[i]);
}
for(int i=1; i<=n; i++){
for(int j=i+1; j<=n; j++){
mp[i][j]=abs((int)(z[i]-z[j]));
mp[j][i]=abs((int)(z[i]-z[j]));
w[i][j]=w[j][i]=sqrt((x[i]-x[j])*(x[i]-x[j])+(y[i]-y[j])*(y[i]-y[j]));
}
}
double L=0, R=(1ll<<30);
for(int i=1; i<=50; i++){
double mid=(L+R)/2;
if(check(mid, n)){
L=mid;
}
else{
R=mid;
}
}
printf("%.3f\n", R);
}

return 0;
}
``````