import sys
input = sys.stdin.readline
# def input(): return sys.stdin.readline().rstrip() # 文字列


def dist(x, y):
    one = x[0] - y[0]
    two = x[1] - y[1]
    return one * one + two * two


n = int(input())
p = [tuple(map(int, input().split())) for i in range(n)]
d = []
for i in range(n - 1):
    for j in range(i + 1, n):
        d.append((dist(p[i], p[j]), i, j))

d.sort(key=lambda x: x[0])
s = set(range(n))
ans = 0
i = 0
while len(s) > 1:
    _, x, y = d[i]
    if x == 0 or y == 0:
        if x + y in s:
            s.remove(x + y)
            ans += 1

    elif x in s and y in s:
        s.remove(x)
        s.remove(y)
    i += 1
print(ans)