#yuki202

n=int(raw_input())
l=[[[] for i in range(600)] for j in range(600)]
res=0
for i in range(n):
 x,y=map(int,raw_input().split())
 ax,ay=(x/40)+1,(y/40)+1
 f=True
 for dx in (-1,0,1):
  for dy in (-1,0,1):
   for bx,by in l[ax+dx][ay+dy]:
    if (bx-x)**2+(by-y)**2<400:
      f=False
      break
 if f:
  res+=1
  l[ax][ay].append((x,y))
print res