import sys
def I(): return int(sys.stdin.readline().rstrip())
def MI(): return map(int,sys.stdin.readline().rstrip().split())

n = I()
x = []
y = []
d = []

a,b = MI()
x.append(a)
y.append(b)

for i in range(1, n):
    a,b = MI()
    x.append(a)
    y.append(b)
    for j in range(i):
        tmp = (x[i]-x[j])**2 + (y[i]-y[j])**2
        d.append((tmp, i, j))

d.sort()

deleted = [1]*n
ans = 0

for i in d:
    if i[2] == 0:
        if deleted[i[1]] == 1:
            deleted[i[1]] = 0
            ans += 1
    else:
        if deleted[i[1]] == 1 and deleted[i[2]] == 1:
            deleted[i[1]] = 0
            deleted[i[2]] = 0

print(ans)