#include <algorithm>
#include <iostream>
#include <cstdio>
#include <map>
#include <numeric>
#include <cmath>
#include <set>
#include <sstream>
#include <string>
#include <vector>
#include <queue>
#include <stack>
#include <complex>
#include <string.h>
#include <unordered_set>
#include <unordered_map>
#include <bitset>
#include <iomanip>
#include <sys/time.h>
#include <tuple>
#include <random>
using namespace std;

#define endl '\n'
#define ALL(v) (v).begin(), (v).end()
#define RALL(v) (v).rbegin(), (v).rend()
#define UNIQ(v) (v).erase(unique((v).begin(), (v).end()), (v).end())

typedef long long ll;
typedef long double ld;
typedef pair<int, int> P;
typedef complex<double> comp;
typedef vector< vector<ld> > matrix;
struct pairhash {
public:
    template<typename T, typename U>
    size_t operator()(const pair<T, U> &x) const {
	size_t seed = hash<T>()(x.first);
	return hash<U>()(x.second) + 0x9e3779b9 + (seed<<6) + (seed>>2);
    }
};
const int inf = 1e9 + 9;
const ll mod = 1e9 + 7;
const double eps = 5e-8;
const double pi = acos(-1);

int n;
double x[1010], y[1010];
double d[1010][1010];

double dist(int i, int j) {
    return sqrt((x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]));
}

class UnionFind {
private:
    static const int MAX = 1010;
    int par[MAX];
    int r[MAX];
public:
    UnionFind(int n = MAX) {
        for (int i = 0; i < n; i++) {
            par[i] = i;
            r[i] = 0;
        }
    }

    int find(int x) {
        if (par[x] == x) {
            return x;
        } else {
            return par[x] = find(par[x]);
        }
    }

    void unite(int x, int y) {
        x = find(x);
        y = find(y);
        if (x == y) return;
        if (r[x] < r[y]) {
            par[x] = y;
        } else {
            par[y] = x;
            if (r[x] == r[y]) r[x]++;
        }
    }

    bool same(int x, int y) {
        return find(x) == find(y);
    }
};

bool check(int k) {
    UnionFind uf;
    for (int i = 0; i < n; i++) {
        for (int j = i+1; j < n; j++) {
            if (d[i][j] < k*10+eps)
                uf.unite(i, j);
        }
    }
    return uf.same(0, n-1);
}

int solve() {
    for (int i = 0; i < n; i++)
        for (int j = 0; j < n; j++)
            d[i][j] = dist(i, j);

    int lb = 0, ub = 2e8;
    while (ub - lb > 1) {
        int mid = (ub + lb) / 2;
        if (check(mid)) {
            ub = mid;
        } else {
            lb = mid;
        }
    }
    return ub * 10;
}

void input() {
    cin >> n;
    for (int i = 0; i < n; i++) cin >> x[i] >> y[i];
}

int main() {
    ios::sync_with_stdio(false);
    cin.tie(0);
    cout << fixed << setprecision(15);

    input();
    cout << solve() << endl;
}