from collections import defaultdict

class UnionFind():
    def __init__(self, n):
        '''
        UnionFindクラス。nは要素数を表す。
        '''
        self.n = n
        self.parents = [-1] * n

    def find(self, x):
        '''
        要素xを含む集合の親を見つける関数。
        '''
        if self.parents[x] < 0:
            return x
        else:
            self.parents[x] = self.find(self.parents[x])
            return self.parents[x]

    def union(self, x, y):
        '''
        要素xを含む集合と要素yを含む集合を合体する関数。
        基本的には、要素数が多い集合に統合される。
        要素数が同じときは要素yを含む集合に統合される。
        '''
        x = self.find(x)
        y = self.find(y)

        if x == y:
            return

        if self.parents[x] > self.parents[y]:
            x, y = y, x

        self.parents[x] += self.parents[y]
        self.parents[y] = x

    def size(self, x):
        '''
        要素xを含む集合の要素数を出す関数。
        '''
        return -self.parents[self.find(x)]

    def same(self, x, y):
        return self.find(x) == self.find(y)

    def members(self, x):
        root = self.find(x)
        return [i for i in range(self.n) if self.find(i) == root]

    def roots(self):
        return [i for i, x in enumerate(self.parents) if x < 0]

    def group_count(self):
        return len(self.roots())

    def all_group_members(self):
        group_members = defaultdict(list)
        for member in range(self.n):
            group_members[self.find(member)].append(member)
        return group_members

    def __str__(self):
        return '\n'.join(f'{r}: {m}' for r, m in self.all_group_members().items())

from math import sqrt

n = int(input())
if n == 0:
    print(1.0)
    exit()
P = [list(map(int, input().split())) for _ in range(n)]

UF = UnionFind(n)
for i in range(n):
    for j in range(i + 1, n):
        if (P[i][0] - P[j][0])**2 + (P[i][1] - P[j][1])**2 <= 10**2:
            UF.union(i, j)

seen = set()
ans = 2.0
for i in range(n):
    if i in seen:
        continue
    G = UF.members(i)
    for a in range(len(G)):
        f = G[a]
        seen.add(f)
        for b in range(a + 1, len(G)):
            g = G[b]
            seen.add(g)
            d = sqrt((P[f][0] - P[g][0])**2 + (P[f][1] - P[g][1])**2)
            ans = max(ans, d + 2)
print(ans)