#include <bits/stdc++.h>
using namespace std;

#define SZ(a) (int)a.size()
#define ALL(a) a.begin(), a.end()
#define FOR(i, a, b) for (int i = (a); i<(b); ++i)
#define RFOR(i, b, a) for (int i = (b)-1; i>=(a); --i)
#define MP make_pair
#define PB push_back
#define F first
#define S second

typedef long long LL;
typedef pair<int, int> PII;
typedef vector<int> VI;

const int MAX = 1 << 10;

int n;
int x[MAX], y[MAX];
LL d[MAX][MAX];
int timer;
int tin[MAX], fup[MAX];
bool used[MAX];
bool ok;

void dfs(int v, int p, LL m) {
	used[v] = true;
	tin[v] = fup[v] = timer++;
	int cnt = 0;
	FOR(i, 0, n) {
		if (d[v][i] <= m && i != p) {
			if (used[i]) {
				fup[v] = min(fup[v], tin[i]);
			}
			else {
				dfs(i, v, m);
				fup[v] = min(fup[v], fup[i]);
				cnt++;
			}
		}
	}
	if (v != 0 && fup[v] == tin[v] && cnt > 0) {
		ok = false;
	}
}

int main()
{
	ios::sync_with_stdio(false);
	cin.tie(0);
	cin >> n;
	n++;
	FOR(i, 1, n) {
		cin >> x[i] >> y[i];
	}
	FOR(i, 0, n) {
		FOR(j, 0, n) {
			d[i][j] = (LL)(x[j] - x[i]) * (x[j] - x[i]) + (LL)(y[j] - y[i]) * (y[j] - y[i]);
		}
	}
	LL l = 0, r = 2.1e18;
	while (r - l > 1) {
		LL m = (l + r) / 2;
		FOR(i, 0, n) {
			used[i] = false;
		}
		timer = 0;
		ok = true;
		dfs(0, -1, m);
		FOR(i, 0, n) {
			ok &= used[i];
		}
		if (ok) {
			r = m;
		}
		else {
			l = m;
		}
	}
	cout << fixed << setprecision(10) << sqrt(r) << "\n";
	return 0;
}