from collections import *
from itertools import *
from functools import *
from heapq import *
import sys,math
input = sys.stdin.readline

class DSU:
    def __init__(self, n):
        self._n = n
        self.parent_or_size = [-1] * n

    def merge(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        x, y = self.leader(a), self.leader(b)
        if x == y: return x
        if -self.parent_or_size[x] < -self.parent_or_size[y]: x, y = y, x
        self.parent_or_size[x] += self.parent_or_size[y]
        self.parent_or_size[y] = x
        return x

    def same(self, a, b):
        assert 0 <= a < self._n
        assert 0 <= b < self._n
        return self.leader(a) == self.leader(b)

    def leader(self, a):
        assert 0 <= a < self._n
        if self.parent_or_size[a] < 0: return a
        self.parent_or_size[a] = self.leader(self.parent_or_size[a])
        return self.parent_or_size[a]

    def size(self, a):
        assert 0 <= a < self._n
        return -self.parent_or_size[self.leader(a)]

    def groups(self):
        leader_buf = [self.leader(i) for i in range(self._n)]
        result = [[] for _ in range(self._n)]
        for i in range(self._n): result[leader_buf[i]].append(i)
        return [r for r in result if r != []]

N = int(input())
X = [tuple(map(int,input().split())) for _ in range(N)]
D = DSU(N)
for i in range(N-1):
    xi,yi = X[i]
    for j in range(i+1,N):
        xj,yj = X[j]
        if (xi-xj)**2 + (yi-yj)**2 <= 100:
            D.merge(i,j)
ans = 2
if N==0:
    print(1)
    exit()
for g in D.groups():
    
    n = len(g)
    for i in range(n-1):
        xi,yi = X[g[i]]
        for j in range(i+1,n):
            xj,yj = X[g[j]]
            tmp = math.sqrt((xi-xj)**2 + (yi-yj)**2)
            ans = max(ans,tmp+2)
print(ans)