#include <iostream>
#include <cstdio>
#include <vector>
#include <list>
#include <cmath>
#include <fstream>
#include <algorithm>
#include <string>
#include <queue>
#include <set>
#include <map>
#include <complex>
#include <iterator>
#include <cstdlib>
#include <cstring>
#include <sstream>
#include <stack>
#include <climits>
#include <deque>
#include <bitset>
#include <cassert>
#include <ctime>
using namespace std;

typedef long long ll;
typedef pair<int,int> pii;
const int dy[]={-1,0,1,0},dx[]={0,1,0,-1};
// adjust problem by problem
const double EPS=1e-8;
const double PI=acos(-1.0);
#define REP(i,n) for(int i=0;i<(int)n;++i)
#ifdef __GNUC__
#define FOR(i,c) for(__typeof((c).begin())i=(c).begin();i!=(c).end();++i)
int popcount(int n){return __builtin_popcount(n);}
int popcount(ll n){return __builtin_popcountll(n);}
#endif
#ifndef __GNUC__
template<class T> int popcount(T val){
  val = val - ((val >> 1) & 0x55555555);
  val = (val & 0x33333333) + ((val >> 2) & 0x33333333);
  val = (val + (val >> 4)) & 0x0f0f0f0f;
  val += val >> 8;
  val += val >> 16;
  return (int)(val & 0x0000003f);
}
#endif
template<class T>int SIZE(T a){return a.size();}
template<class T>string IntToString(T num){string res;stringstream ss;ss<<num;return ss.str();}
template<class T>T StringToInt(string str){T res=0;for(int i=0;i<SIZE(str);i++)res=(res*10+str[i]-'0');return res;}
template<class T>T gcd(T a,T b){if(b==0)return a;return gcd(b,a%b);}
template<class T>T lcm(T a,T b){return a/gcd(a,b)*b;}
template<class T> void PrintSeq(T &a,int sz){for(int i=0;i<sz;i++){cout<<a[i];if(sz==i+1)cout<<endl;else cout<<' ';}}
ll getTen(int a){return (a<=0)?1:(getTen(a-1)*10);}
bool EQ(double a,double b){return abs(a-b)<EPS;}
void fastStream(){cin.tie(0);std::ios_base::sync_with_stdio(0);}
vector<string> split(string str,char del){
  vector<string> res;
  for(int i=0,s=0;i<SIZE(str);i++){
    if(str[i]==del){if(i-s!=0)res.push_back(str.substr(s,i-s));s=i+1;}
    else if(i==SIZE(str)-1){res.push_back(str.substr(s));}
  }
  return res;
}

int N;
double sy,sx,sz;
double gy,gx,gz;
double px[101][2];
double py[101][2];
double pz[101][2];
double d[101][101];

struct Point{
  double x,y,z;
  Point(){}
  Point(double x_,double y_,double z_){
    x=x_,y=y_,z=z_;
  }
  Point operator-(const Point &p)const{
    return Point(x-p.x,y-p.y,z-p.z);
  }
  Point operator+(const Point &p)const{
    return Point(x+p.x,y+p.y,z+p.z);
  }
  Point operator/(double d)const{
    return Point(x/d,y/d,z/d);
  }
  string ToString(){
    string res;
    {
      stringstream ss;
      ss<<x;
      res+=ss.str();
    }
    res+=' ';
    {
      stringstream ss;
      ss<<y;
      res+=ss.str();
    }
    res+=' ';
    {
      stringstream ss;
      ss<<z;
      res+=ss.str();
    }
    return res;
  }
};

double dot(Point p1,Point p2){
  return p1.x*p2.x+p1.y*p2.y+p1.z*p2.z;
}
Point cross(Point p1,Point p2){
  return Point(p1.y*p2.z-p1.z*p2.y,p1.z*p2.x-p1.x*p2.z,p1.x*p2.y-p1.y*p2.x);
}
double abs(Point p){
  return sqrt(p.x*p.x+p.y*p.y+p.z*p.z);
}

double calcDist(Point p1,Point p2,Point p3,Point p4){
  Point n=cross(p2-p1,p4-p3);
  Point c=(p3-p1);
  if(!EQ(abs(n),0))return abs(dot(n,c))/abs(n);
  else {
    Point x=p3-p1;
    Point y=(p2-p1)/abs(p2-p1);
    return abs(cross(x,y));
  }
}

int main(){

  while(cin>>N&&N){
    cin>>sx>>sy>>sz>>gx>>gy>>gz;
    for(int i=0;i<N;i++)
      for(int j=0;j<2;j++)
        cin>>px[i][j]>>py[i][j]>>pz[i][j];
    for(int i=0;i<N;i++){
      for(int j=i;j<N;j++){
        if(i==j)d[i][j]=0;
        else d[i][j]=d[j][i]=calcDist(Point(px[i][0],py[i][0],pz[i][0])
                                      ,Point(px[i][1],py[i][1],pz[i][1])
                                      ,Point(px[j][0],py[j][0],pz[j][0])
                                      ,Point(px[j][1],py[j][1],pz[j][1]));
      }
    }
    for(int k=0;k<N;k++)
      for(int i=0;i<N;i++)
        for(int j=0;j<N;j++)
          d[i][j]=min(d[i][j],d[i][k]+d[k][j]);
    int spos=-1,gpos=-1;
    for(int i=0;i<N;i++){
      if(EQ(0,calcDist(Point(px[i][0],py[i][0],pz[i][0]),Point(px[i][1],py[i][1],pz[i][1])
                       ,Point(sx,sy,sz),Point(sx,sy,sz))))spos=i;
      if(EQ(0,calcDist(Point(px[i][0],py[i][0],pz[i][0]),Point(px[i][1],py[i][1],pz[i][1])
                       ,Point(gx,gy,gz),Point(gx,gy,gz))))gpos=i;
    }
    printf("%.10f\n",d[spos][gpos]);
  }
  
  
  return 0;
}

Measured memory_bytes: 1336