Balloon

const double EPS = 1e-9;
const int MAXV = 100010;
struct TwoSAT
{
    int n;
    vector<int> G[MAXV*2];
    bool mark[MAXV*2];
    int S[MAXV*2], c;

    void init(int n)
    {
        this->n = n;
        for (int i = 0; i < n*2; i++) G[i].clear();
        memset(mark, 0, sizeof(mark));
    }

    bool dfs(int x)
    {
        if (mark[x^1]) return false;
        if (mark[x]) return true;
        mark[x] = true;
        S[c++] = x;
        for (int i = 0; i < G[x].size(); i++)
            if (!dfs(G[x][i])) return false;
        return true;
    }

    // x = xval or y = yval
    void add_clause(int x, int xval, int y, int yval)
    {
        x = x * 2 + xval;
        y = y * 2 + yval;
        G[x^1].push_back(y);
        G[y^1].push_back(x);
    }

    bool solve()
    {
        for(int i = 0; i < n*2; i += 2)
            if(!mark[i] && !mark[i+1])
            {
                c = 0;
                if(!dfs(i))
                {
                    while(c > 0) mark[S[--c]] = false;
                    if(!dfs(i+1)) return false;
                }
            }
        return true;
    }
} tst;

int n, m;
struct Point
{
    double x, y, z;
    inline void read()
    {
        scanf("%lf%lf%lf", &x, &y, &z);
    }
} ipt[MAXN][2];

inline double dis(Point pa, Point pb)
{
    return sqrt(sqr(pa.x - pb.x) + sqr(pa.y - pb.y) + sqr(pa.z - pb.z));
}
bool check(double Min)
{
    tst.init(n);
    REP(i, n) FF(j, i + 1, n)
    {
        REP(ii, 2) REP(jj, 2)
        {
            double d = dis(ipt[i][ii], ipt[j][jj]);
            if (d < Min)
            {
                tst.add_clause(i, ii ^ 1, j, jj ^ 1);
            }
        }
    }
    return tst.solve();
}

int main()
{
    while (~RI(n))
    {
        REP(i, n) REP(j, 2)
            ipt[i][j].read();
        double l = 0, r = 1e20, m;
        while (l + EPS < r)
        {
            m = (l + r) / 2;
            if (check(m * 2))
                l = m;
            else
                r = m;
        }
        printf("%.3f\n", (int)(r * 1000) / 1000.0);
    }
    return 0;
}