n = int(input())
x = [0] * n
y = [0] * n
for i in range(n):
    x[i], y[i] = map(int, input().split())


def dist(i, j):
    return (x[j] - x[i]) ** 2 + (y[j] - y[i]) ** 2


d = []
for i in range(n):
    for j in range(i + 1, n):
        if i == j:
            continue
        d.append((dist(i, j), i, j))
d.sort()

used = [False] * n
ans = 0
for _, i, j in d:
    if i == 0:
        if not used[j]:
            ans += 1
            used[j] = True
    else:
        if not used[j] and not used[i]:
            used[i] = True
            used[j] = True
print(ans)