#include "bits/stdc++.h"
#define ALL(obj) (obj).begin(),(obj).end()
#define RALL(obj) (obj).rbegin(),(obj).rend()
#define REP(i, n) for(int i = 0; i < (int)(n); i++)
#define REPR(i, n) for(int i = (int)(n); i >= 0; i--)
#define FOR(i,n,m) for(int i = (int)(n); i < int(m); i++)
using namespace std;
typedef long long ll;
const int MOD = 1e9 + 7;
const int INF = MOD - 1;
const ll LLINF = 4e18;

//UnionFind
class UnionFind {
private:
    vector<int> par;
public:
    UnionFind(int n) {
        par.resize(n, -1);
    }

    int root(int x) {
        if (par[x] < 0) return x;
        return par[x] = root(par[x]);
    }

    bool unite(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        if (rx == ry) return false;
        if (size(rx) < size(ry)) swap(rx, ry);
        par[rx] += par[ry];
        par[ry] = rx;
        return true;
    }

    bool same(int x, int y) {
        int rx = root(x);
        int ry = root(y);
        return rx == ry;
    }

    int size(int x) {
        return -par[root(x)];
    }
};

int main() {
    int n; cin >> n;
    vector<int> x(n), y(n);
    UnionFind uni(n);
    REP(i, n) {
        cin >> x[i] >> y[i];
    }
    REP(i, n-1) {
        FOR(j, i + 1, n) {
            int d = (x[i] - x[j])*(x[i] - x[j]) + (y[i] - y[j])*(y[i] - y[j]);
            if (d <= 100) {
                uni.unite(i, j);
            }
        }
    }
    double ans = -1;
    REP(i, n - 1) {
        FOR(j, i, n) {
            if (uni.same(i, j)) {
                int d = (x[i] - x[j])*(x[i] - x[j]) + (y[i] - y[j])*(y[i] - y[j]);
                ans = max(ans, sqrt(d));
            }
        }
    }
    if (n == 1) {
        puts("2");
    }
    else {
        printf("%.10f", ans + 2);
    }
    getchar(); getchar();
}