n = int(input())
P = [list(map(int, input().split())) for _ in range(n)]

L = []
for i in range(n):
    for j in range(i + 1, n):
        L.append(((P[i][0] - P[j][0])**2 + (P[i][1] - P[j][1])**2, i, j))

L.sort()
seen = set()
ans = 0
for _, i, j in L:
    if i == 0:
        if j in seen:
            continue
        ans += 1
        seen.add(j)
    else:
        if i in seen or j in seen:
            continue
        seen.add(i)
        seen.add(j)
print(ans)