import sys
readline = sys.stdin.readline

def dis(i, j):
    return abs(Points[i][0]-Points[j][0])**2 + abs(Points[i][1]-Points[j][1])**2

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

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