import sys,heapq
input = sys.stdin.buffer.readline
n=int(input())

par=[-1]*n

def find(x):
  if par[x]<0:
    return x
  else:
    par[x]=find(par[x])
    return par[x]

def unite(x,y):
  x=find(x)
  y=find(y)
  if x==y:
    return False
  else:
    if par[x]>par[y]:
      x,y=y,x
    par[x]+=par[y]
    par[y]=x
    return True

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

def size(x):
  return -par[find(x)]

import heapq
XY=[]
for _ in range(n):
  XY.append(tuple(int(i) for i in input().split()))
Q=[]
eps=0.0001
def f(x1,y1,x2,y2):
  return ((int(((x2-x1)**2+(y2-y1)**2)**0.5+eps)-1)//10+1)*10
for i in range(n-1):
  for j in range(i+1,n):
    heapq.heappush(Q,(f(XY[i][0],XY[i][1],XY[j][0],XY[j][1]),i,j))
ans=0
while True:
  d,i,j=heapq.heappop(Q)
  if not same(i,j):
    ans=max(ans,d)
    unite(i,j)
  if same(0,n-1):
    break
print(ans)