import sys
readline = sys.stdin.readline
from operator import itemgetter


N = int(readline())
Points = [tuple(map(int, readline().split())) for _ in range(N)]

dis = [[0]*N for _ in range(N)]
for i in range(N):
    x, y = Points[i]
    for j in range(i):
        x1, y1 = Points[j]
        dis[i][j] = (x-x1)*(x-x1) + (y-y1)*(y-y1)

K = [(dis[i][j]*1000+N-1-j, i, j) for i in range(N) for j in range(i)]
K.sort(key = itemgetter(0))
vanish = set()
ans = 0
for _, i, j in K:
    if j == 0:
        if i not in vanish:
            vanish.add(i)
            ans += 1
        continue
    if i not in vanish and j not in vanish:
        vanish.add(i)
        vanish.add(j)

print(ans)