#include <bits/stdc++.h>
using namespace std;
#ifdef LOCAL
#include "debug.h"
#else
#define dump(...)
#endif
#define endl "\n"
#define ll long long
#define int ll
#define float double
#define FOR(i, a, b) for (int i = (int)(a); i < (int)(b); i++)
#define REP(i, x) for (int i = 0; i < (int)(x); i++)
#define REPS(i, x) for (int i = 1; i <= (int)(x); i++)
#define RREP(i, x) for (int i = ((int)(x)-1); i >= 0; i--)
#define RREPS(i, x) for (int i = ((int)(x)); i > 0; i--)
#define INF (1 << 30 - 1)
#define LLINF (1LL << 60)
#define vi vector<int>
#define vvi vector<vector<int>>
#define pi pair<int, int>
#define ALL(a) (a).begin(), (a).end()
#define BIT(n) (1LL << (n))
#define UNIQUE(v) v.erase(unique(v.begin(), v.end()), v.end()) //sortしてからつかうこと
constexpr ll MOD = 1e9 + 7;
int dx[8] = {1, 0, -1, 0, 1, 1, -1, -1};
int dy[8] = {0, 1, 0, -1, 1, -1, 1, -1};
ll A, B, C, D, E, F, G, H, N, M, L, K, P, Q, R, W, X, Y, Z;
string S, T;
ll ans = 0;

template <typename T>
istream &operator>>(istream &is, vector<T> &vec) {
    for (T &x : vec)
        is >> x;
    return is;
}

template <typename T>
class Vec3 {
public:
    T x = 0, y = 0, z = 0;
    Vec3() {}
    Vec3(T x, T y, T z) : x(x), y(y), z(z) {}

    bool operator==(const Vec3 &other) const {
        return x == other.x && y == other.y && z == other.z;
    }
    bool operator!=(const Vec3 &other) const {
        return x != other.x || y != other.y || z != other.z;
    }

    Vec3 &operator+=(const Vec3 &other) {
        x += other.x;
        y += other.y;
        z += other.z;
        return *this;
    }

    Vec3 &operator-=(const Vec3 &other) {
        x -= other.x;
        y -= other.y;
        z -= other.z;
        return *this;
    }

    Vec3 &operator*=(const T k) {
        x *= k;
        y *= k;
        z *= k;
        return *this;
    }

    Vec3 &operator/=(const T k) {
        x /= k;
        y /= k;
        z /= k;
        return *this;
    }

    Vec3 &operator=(const Vec3 &other) {
        x = other.x;
        y = other.y;
        z = other.z;
        return *this;
    }

    Vec3 operator+(const Vec3 &other) const {
        Vec3 res = *this;
        return res += other;
    }

    Vec3 operator-(const Vec3 &other) const {
        Vec3 res = *this;
        return res -= other;
    }

    Vec3 operator*(const T k) const {
        Vec3 res = *this;
        return res *= k;
    }

    Vec3 operator/(const T k) const {
        Vec3 res = *this;
        return res /= k;
    }

    T norm() {
        return sqrt(x * x + y * y + z * z);
    }

    T snorm() {
        return (x * x + y * y + z * z);
    }

    T dot(const Vec3 &other) const {
        return x * other.x + y * other.y + z * other.z;
    }

    Vec3 cross(const Vec3 &other) {
        Vec3 res;
        res.x = y * other.z - other.y * z;
        res.y = z * other.x - other.z * x;
        res.z = x * other.y - other.x * y;
        return res;
    }

    void normalize() {
        T n = this->norm();
        *this /= n;
    }
};

template <typename T>
Vec3<T> operator*(const T k, Vec3<T> &v) {
    Vec3<T> res = v;
    return res *= k;
}

template <typename T>
Vec3<T> operator/(const T k, Vec3<T> &v) {
    Vec3<T> res = v;
    return res /= k;
}

using Vec3f = Vec3<float>;
using Vec3d = Vec3<double>;

#define NMAX 20

class SortCell {
public:
    int listN;
    int *index_list;

    SortCell *child;

    SortCell() {
        listN = 0;
        index_list = NULL;
        child = NULL;
    }

    ~SortCell() {
        if (listN != 0)
            delete index_list;
        if (child != NULL)
            delete[] child;
    }

    void addIndex(int index) {
        int *tmp = new int[listN + 1];
        for (int i = 0; i < listN; i++)
            tmp[i] = index_list[i];
        if (listN != 0)
            delete[] index_list;
        index_list = tmp;
        index_list[listN++] = index;
    }

    void crerateChild() {
        child = new SortCell[8];
    }
};

class PointSet {
public:
    int pointN;
    float (*point)[3];
    float (*normal)[3];
    float size;

private:
    SortCell sort_root;
    float sort_center[3];
    float sort_size;
    int *collect_list;
    int collect_listN;

public:
    PointSet(int pN, float (*p)[3], float (*n)[3]) {
        pointN = pN;
        point = p;
        normal = n;

        collect_list = new int[pointN];

        sort();
        size = sort_size * 2;
    }

    ~PointSet() {
        delete[] collect_list;
    }

    int collect(int *&index, float v[3], float r) {
        collect_listN = 0;
        collect(v, r, &sort_root, sort_center, sort_size);

        index = collect_list;
        return collect_listN;
    }

private:
    void sort() {
        float min[3], max[3];
        bound(min, max);

        for (int i = 0; i < 3; i++)
            sort_center[i] = 0.5f * (min[i] + max[i]);

        sort_size = max[0] - min[0];
        if (sort_size < max[1] - min[1])
            sort_size = max[1] - min[1];
        if (sort_size < max[2] - min[2])
            sort_size = max[2] - min[2];
        sort_size *= 0.6f;

        for (int i = 0; i < pointN; i++)
            sort(i, &sort_root, sort_center, sort_size);
    }

    void bound(float min[3], float max[3]) {
        max[0] = min[0] = point[0][0];
        max[1] = min[1] = point[0][1];
        max[2] = min[2] = point[0][2];
        for (int i = 1; i < pointN; i++) {
            if (max[0] < point[i][0])
                max[0] = point[i][0];
            if (max[1] < point[i][1])
                max[1] = point[i][1];
            if (max[2] < point[i][2])
                max[2] = point[i][2];

            if (min[0] > point[i][0])
                min[0] = point[i][0];
            if (min[1] > point[i][1])
                min[1] = point[i][1];
            if (min[2] > point[i][2])
                min[2] = point[i][2];
        }
    }

    void sort(int index, SortCell *cell, float *c, float s) {
        if (cell->child == NULL) {
            if (cell->listN < NMAX)
                cell->addIndex(index);
            else {
                cell->crerateChild();
                for (int i = 0; i < NMAX; i++)
                    sort(cell->index_list[i], cell, c, s);
                delete[] cell->index_list;
                cell->listN = 0;

                sort(index, cell, c, s);
            }
        } else {
            int i = 0;
            float c1[3], s1;
            s1 = 0.5f * s;
            if (point[index][0] > c[0]) {
                i += 1;
                c1[0] = c[0] + s1;
            } else
                c1[0] = c[0] - s1;

            if (point[index][1] > c[1]) {
                i += 2;
                c1[1] = c[1] + s1;
            } else
                c1[1] = c[1] - s1;

            if (point[index][2] > c[2]) {
                i += 4;
                c1[2] = c[2] + s1;
            } else
                c1[2] = c[2] - s1;

            sort(index, &(cell->child[i]), c1, s1);
        }
    }

    void collect(float *p, float r, SortCell *cell, float *c, float s) {
        if (p[0] + r < c[0] - s || p[1] + r < c[1] - s || p[2] + r < c[2] - s ||
            p[0] - r > c[0] + s || p[1] - r > c[1] + s || p[2] - r > c[2] + s)
            return;

        if (cell->child == NULL) {
            for (int i = 0; i < cell->listN; i++) {
                int j = cell->index_list[i];
                float *q = point[j];
                float vx = q[0] - p[0];
                float vy = q[1] - p[1];
                float vz = q[2] - p[2];
                if (vx * vx + vy * vy + vz * vz > r * r)
                    continue;
                collect_list[collect_listN++] = j;
            }
            return;
        }

        float c1[3], s1;
        s1 = 0.5f * s;

        c1[0] = c[0] - s1;
        c1[1] = c[1] - s1;
        c1[2] = c[2] - s1;
        collect(p, r, &(cell->child[0]), c1, s1);

        c1[0] = c[0] + s1;
        collect(p, r, &(cell->child[1]), c1, s1);

        c1[0] = c[0] - s1;
        c1[1] = c[1] + s1;
        collect(p, r, &(cell->child[2]), c1, s1);

        c1[0] = c[0] + s1;
        collect(p, r, &(cell->child[3]), c1, s1);

        c1[0] = c[0] - s1;
        c1[1] = c[1] - s1;
        c1[2] = c[2] + s1;
        collect(p, r, &(cell->child[4]), c1, s1);

        c1[0] = c[0] + s1;
        collect(p, r, &(cell->child[5]), c1, s1);

        c1[0] = c[0] - s1;
        c1[1] = c[1] + s1;
        collect(p, r, &(cell->child[6]), c1, s1);

        c1[0] = c[0] + s1;
        collect(p, r, &(cell->child[7]), c1, s1);
    }
};

#undef NMAX

signed main() {
    cin >> N;
    vector<Vec3f> pts(N);
    float(*points)[3] = new float[N][3];
    float(*norms)[3] = new float[N][3];
    vector<float> rads;
    for (int i = 0; i < N; i++) {
        cin >> pts[i].x >> pts[i].y;
        points[i][0] = pts[i].x;
        points[i][1] = pts[i].y;
        points[i][2] = 0;
        norms[i][0] = 0;
        norms[i][1] = 0;
        norms[i][2] = 0;
    }
    vector<Vec3f> ofs;
    for (int i = 0; i < N; i++) {
        for (int j = i + 1; j < N; j++) {
            ofs.push_back((pts[i] + pts[j]) / 2.0);
            rads.push_back((pts[i] - pts[j]).norm() / 2.0);
            for (int k = j + 1; k < N; k++) {
                Vec3f v1 = pts[j] - pts[i];
                Vec3f v2 = pts[k] - pts[i];
                Vec3f v3 = pts[j] - pts[k];
                rads.push_back(v3.norm() / 2.0 / (abs(v1.cross(v2).z) / (v1.norm() * v2.norm())));
                Vec3f tmp;
                tmp.x = (pts[i].snorm() * (pts[j].y - pts[k].y) + pts[j].snorm() * (pts[k].y - pts[i].y) + pts[k].snorm() * (pts[i].y - pts[j].y)) / (pts[i].x * (pts[j].y - pts[k].y) + pts[j].x * (pts[k].y - pts[i].y) + pts[k].x * (pts[i].y - pts[j].y)) / 2.0f;
                tmp.y = -(pts[i].snorm() * (pts[j].x - pts[k].x) + pts[j].snorm() * (pts[k].x - pts[i].x) + pts[k].snorm() * (pts[i].x - pts[j].x)) / (pts[i].x * (pts[j].y - pts[k].y) + pts[j].x * (pts[k].y - pts[i].y) + pts[k].x * (pts[i].y - pts[j].y)) / 2.0f;
                ofs.push_back(tmp);
            }
        }
    }
    PointSet ps(N, points, norms);
    float ans = 1000 * 1000 * 1000;
    dump(rads);
    for (int i = 0; i < rads.size(); i++) {
        int *index;
        float v[3] = {ofs[i].x, ofs[i].y, ofs[i].z};
        int num = ps.collect(index, v, rads[i] + 1e-8);
        if (num == N) {
            dump(num, rads[i]);
            ans = min(ans, rads[i]);
        }
    }
    cout << setprecision(10) << ans << endl;
}

Measured memory_bytes: 1340