import sys, re
from collections import deque, defaultdict, Counter
from math import ceil, sqrt, hypot, factorial, pi, sin, cos, radians, gcd
from itertools import accumulate, permutations, combinations, product, groupby, combinations_with_replacement
from operator import itemgetter, mul
from copy import deepcopy
from string import ascii_lowercase, ascii_uppercase, digits
from bisect import bisect, bisect_left
from heapq import heappush, heappop
from functools import reduce
def input(): return sys.stdin.readline().strip()
def INT(): return int(input())
def MAP(): return map(int, input().split())
def LIST(): return list(map(int, input().split()))
def ZIP(n): return zip(*(MAP() for _ in range(n)))
sys.setrecursionlimit(10 ** 9)
INF = float('inf')
mod = 10 ** 9 + 7

N = INT()
xy = [LIST() for _ in range(N)]

dist = []
for i, j in combinations(range(N), 2):
    x1, y1 = xy[i]
    x2, y2 = xy[j]
    d = (x1-x2)**2 + (y1-y2)**2
    dist.append((d, i, j))

dist.sort()

ans = 0
s = set()

for _, i, j in dist:
    if i in s or j in s:  # 既に爆発済み
        continue
    elif i == 0:  # 取り除く
        ans += 1
        s.add(j)
    else:  # 爆発
        s.add(i)
        s.add(j)

print(ans)