n = int(input())
xy = [list(map(int, input().split())) for i in range(n)]
l = []
for i in range(n):
    for j in range(i + 1, n):
        l.append(((xy[i][0] - xy[j][0]) ** 2 + (xy[i][1] - xy[j][1]) ** 2, i, j))
visited = [False] * n
l.sort()
ans = 0
for d, i, j in l:
    if i == 0:
        if not visited[j]:
            ans += 1
            visited[j] = True
    else:
        if not visited[i] and not visited[j]:
            visited[i] = True
            visited[j] = True
print(ans)