def distance(X, Y):
    return abs(X[0] - Y[0])**2 + abs(X[1] - Y[1])**2

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

for i in range(n):
    for g in range(i+1, n):
        d.append((distance(xy[i], xy[g]), (i, g)))
d.sort()

cnt = 0
used = [False]*n

for i, x in d:
    if used[x[0]] or used[x[1]]:
        continue
    if x[0] == 0:
        cnt += 1
        used[x[1]] = True
    else:
        used[x[0]] = True
        used[x[1]] = True

print(cnt)