#include #include #include #include #include /* * Union-Find tree * header requirement: vector */ class UnionFind { private: std::vector disj; std::vector rank; public: UnionFind(int n) : disj(n), rank(n) { for (int i = 0; i < n; ++i) { disj[i] = i; rank[i] = 0; } } int root(int x) { if (disj[x] == x) { return x; } return disj[x] = root(disj[x]); } void unite(int x, int y) { x = root(x); y = root(y); if (x == y) { return; } if (rank[x] < rank[y]) { disj[x] = y; } else { disj[y] = x; if (rank[x] == rank[y]) { ++rank[x]; } } } bool is_same_set(int x, int y) { return root(x) == root(y); } }; #define REP(i,s,n) for(int i=(int)(s);i<(int)(n);i++) using namespace std; typedef long long int ll; typedef vector VI; const double EPS=1e-9; const int N = 120001; int x[N], y[N]; const int W = 2100; const int B = 10; const int TH = 420; VI board[W][W]; ll solve(const vector &t) { int n = t.size(); ll ma = 0; if (n <= TH) { REP(j, 0, n) { REP(k, j + 1, n) { int a = t[j]; int b = t[k]; ll dist = (x[a] - x[b]) * (x[a] - x[b]) + (y[a] - y[b]) * (y[a] - y[b]); ma = max(ma, dist); } } return ma; } // rotation REP(i, 0, TH) { double pi = acos(-1.0); double s = sin(2 * pi * i / TH); double c = cos(2 * pi * i / TH); typedef pair PDI; vector ss(n); REP(i, 0, n) { ss[i] = PDI(c * x[t[i]] + s * y[t[i]], i); } sort(ss.begin(), ss.end()); int u = ss[0].second; int v = ss[ss.size() - 1].second; ma = max(ma, ll(x[u] - x[v]) * (x[u] - x[v]) + (y[u] - y[v]) * (y[u] - y[v])); } return ma; } int main(void){ int n; cin >> n; if (n == 0) { cout << 1 << endl; return 0; } const int BIAS = 10000; UnionFind uf(n); REP(i, 0, n) { cin >> x[i] >> y[i]; x[i] += BIAS; y[i] += BIAS; board[x[i] / B][y[i] / B].push_back(i); } REP(i, 0, n) { REP(a, -1, 2) { REP(b, -1, 2) { if (x[i] / B + a < 0 || y[i] / B + b < 0) { continue; } VI &neighbor = board[x[i] / B + a][y[i] / B + b]; REP(k, 0, neighbor.size()) { int j = neighbor[k]; int dist = (x[i] - x[j]) * (x[i] - x[j]) + (y[i] - y[j]) * (y[i] - y[j]); if (dist <= 100) { uf.unite(i, j); } } } } } ll ma = 0; vector conn(n); REP(i, 0, n) { conn[uf.root(i)].push_back(i); } REP(i, 0, n) { VI &t = conn[i]; ma = max(ma, solve(t)); } printf("%.15f\n", 2 + sqrt(ma)); }