from operator import itemgetter
from itertools import *
from bisect import *
from collections import *
from heapq import *
import sys

# input=sys.stdin.buffer.readline
input=sys.stdin.readline

sys.setrecursionlimit(10**6)
int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(input())
def MI(): return map(int, input().split())
def MI1(): return map(int1, input().split())
def LI(): return list(map(int, input().split()))
def LI1(): return list(map(int1, input().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
def SI(): return input()[:-1]
def LLI1(rows_number): return [LI1() for _ in range(rows_number)]
dij = [(1, 0), (0, 1), (-1, 0), (0, -1)]

n=II()
xy=LLI(n)
dij=[]
for i,(x0,y0) in enumerate(xy):
    for j,(x1,y1) in enumerate(xy[:i]):
        dij.append(((x0-x1)**2+(y0-y1)**2,i,j))
dij.sort()
fin=[False]*n
ans=0
for d,i,j in dij:
    if fin[i] or fin[j]:continue
    if i==0 or j==0:
        fin[i+j]=True
        ans+=1
        n-=1
    else:
        fin[i]=fin[j]=True
        n-=2
    if n==1:break

print(ans)