1 //#pragma comment(linker, "/STACK:16777216") //for c++ Compiler 2 #include <stdio.h> 3 #include <iostream> 4 #include <cstring> 5 #include <cmath> 6 #include <stack> 7 #include <queue> 8 #include <vector> 9 #include <algorithm>10 #define ll long long11 #define Max(a,b) (((a) > (b)) ? (a) : (b))12 #define Min(a,b) (((a) < (b)) ? (a) : (b))13 #define Abs(x) (((x) > 0) ? (x) : (-(x)))14 using namespace std;15 16 const int INF = 0x3f3f3f3f;17 const int MAXN = 220;18 const double eps = 1e-8;19 int n;20 struct POINT{21     double x,y,z;22 }ps[35],q;23 24 double dist(POINT a,POINT b){25     return sqrt((a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z));26 }27 28 int maxD(POINT p){29     double res = 0;30     int i, k = 0;31     for(i = 0; i < n ; ++i){32         double tmp = dist(p,ps[i]);33         if(tmp > res){34             k = i;35             res = dist(p,ps[i]);36         }37     }38     return k;39 }40 41 double BallCover(){42     double step = 100, ans = INF;43     q.x = q.y = q.z = 0.0;44     while(step > eps){45         int d = maxD(q);46         double tmp = dist(ps[d],q);47         if(tmp < ans) ans=tmp;48         double dx = ps[d].x - q.x;49         double dy = ps[d].y - q.y;50         double dz = ps[d].z - q.z;51         dx /= tmp;52         dy /= tmp;53         dz /= tmp;54         q.x += (dx*step);55         q.y += (dy*step);56         q.z += (dz*step);57         step *= 0.98;58     }59     return ans;60 }61 62 int main(){63     int i;64     while(EOF != scanf("%d",&n)){65         if(0 == n)  break;66         for(i = 0; i < n ; ++i)67             scanf("%lf%lf%lf",&ps[i].x,&ps[i].y,&ps[i].z);68         printf("%.5f\n",BallCover());69     }70     return 0;71 }