#!/usr/bin/env python3
# -*- coding: utf-8 -*-

import array
import collections
import itertools


EPS = 10 ** (-9)


Station = collections.namedtuple("Station", "index coordinate")


class UnionFind(object):

    def __init__(self, number_of_nodes):
        self.par = array.array("L", range(number_of_nodes))
        self.rank = array.array("L", (0 for i in range(number_of_nodes)))

    def root(self, node):
        if self.par[node] == node:
            return node
        else:
            r = self.root(self.par[node])
            self.par[node] = r
            return r

    def in_the_same_set(self, node1, node2):
        return self.root(node1) == self.root(node2)

    def unite(self, node1, node2):
        x = self.root(node1)
        y = self.root(node2)
        if x == y:
            pass
        elif self.rank[x] < self.rank[y]:
            self.par[x] = y
        else:
            self.par[y] = x
            if self.rank[x] == self.rank[y]:
                self.rank[x] += 1


def main():
    n = int(input())
    if n == 0:
        print("{:.12f}".format(1.0))
        return
    elif n == 1:
        print("{:.12f}".format(2.0))
        return
    stations = [Station(i, complex(*map(int, input().split())))
                for i in range(n)]
    uf = UnionFind(n)
    for st1, st2 in itertools.combinations(stations, 2):
        if abs(st1.coordinate - st2.coordinate) < 10.0 + EPS:
            uf.unite(st1.index, st2.index)
    answer = 2.0
    for st1, st2 in itertools.combinations(stations, 2):
        if uf.in_the_same_set(st1.index, st2.index):
            answer = max(answer, 2.0 + abs(st1.coordinate - st2.coordinate))
    print("{:.12f}".format(answer))


if __name__ == '__main__':
    main()