#include<bits/stdc++.h>
#define int long long
#define For(i, a, b) for (register int i = (a); i <= (b); ++i)
#define Rof(i, a, b) for (register int i = (a); i >= (b); --i)
#define For_Edge(i, x) for(register int i = head[x]; i; i = edge[i].nex)
#define fi first
#define se second
using namespace std;
inline int read() {
    int x = 0;
    char c = getchar();
    bool f = 0;
    while(!isdigit(c)) f |= (c == '-'), c = getchar();
    while(isdigit(c)) x = (x * 10) + (c ^ 48), c = getchar();
    return f ? -x : x;
}
inline void Checkmin(int &x, int y) { x = x < y ? x : y; }
inline void Checkmax(int &x, int y) { x = x > y ? x : y; }
const int maxn = 55;
const double INF = 1e18 + 7.0;
int n;
double Answer;
struct node {
    int x, y, z;
}Point[maxn];
inline node operator - (node x, node y) { return (node){x.x - y.x, x.y - y.y, x.z - y.z}; }
inline int operator ^ (node x, node y) { return x.x * y.x + x.y * y.y + x.z * y.z; }
inline node operator * (node x, node y) { return (node){x.y * y.z - x.z * y.y, x.z * y.x - x.x * y.z, x.x * y.y - x.y * y.x}; }
inline void Init() {
    n = read();
    For(i, 1, n) Point[i].x = read(), Point[i].y = read(), Point[i].z = read();
}
inline void Calc(node P) {
    if(!(P ^ P)) return ;
    int minn = INF, maxx = -INF;
    For(i, 1, n) Checkmin(minn, P ^ Point[i]), Checkmax(maxx, P ^ Point[i]);
    Answer = fmin(Answer, 1.0 * (maxx - minn) / sqrt(1.0 * (P ^ P)));
}
inline void Solve() {
    Answer = INF;
    For(i, 1, n) {
        For(j, i + 1, n) {
            For(i2, i, n) {
                For(j2, i2 + 1, n) {
                    node P1 = Point[j] - Point[i], P2 = Point[j2] - Point[i2], P = P1 * P2;
                    Calc(P);
                }
            }
        }
    }
    if(Answer >= INF) printf("-1\n");
    else printf("%0.12lf\n", Answer);
}
signed main() {
//    freopen("J.in", "r", stdin);
//    freopen("J.out", "w", stdout);
    Init(), Solve();
    return 0;
}