#include<cstdio>
#include<cmath>
#include<algorithm>
using namespace std;
const double eps=1e-3;
int n;
struct Point{
    double x;
    double y;
    double z;
    Point(double _x=0.0,double _y=0.0,double _z=0.0){x=_x;y=_y;z=_z;}
};
Point points[105];
inline double dis(Point a,Point b)
{
    double norm=(a.x-b.x)*(a.x-b.x)+(a.y-b.y)*(a.y-b.y)+(a.z-b.z)*(a.z-b.z);
    return sqrt(norm);
}
double solve()
{
    double T=1000.0; //初始温度
    double rate=0.99999; //温度下降系数
    Point ans_p;    //初始圆心
    int cur;
    Point max_p; //距离圆心最远的点
    double ans=1e99;
    while(T>eps) //模拟降温
    {
        double max_dis=0.0; //选定圆心到最远点距离
        for(int i=1;i<=n;++i)
        { //最远的点即points[cur]
            if(dis(ans_p,points[i])>max_dis){
                max_dis=dis(ans_p,points[i]);
                cur=i;
            }
        }
        ans=min(ans,max_dis);
        ans_p.x+=(points[cur].x-ans_p.x)*(T/1000.0);
        ans_p.y+=(points[cur].y-ans_p.y)*(T/1000.0);
        ans_p.z+=(points[cur].z-ans_p.z)*(T/1000.0);
        T*=rate;
    }
    return ans;
}
int main()
{
    while(scanf("%d",&n)!=EOF)
    {
        for(int i=1;i<=n;++i)
        {
            scanf("%lf%lf%lf",&points[i].x,&points[i].y,&points[i].z);
        }
        printf("%.15f\n",solve());
    }
    return 0;
}