"""

https://yukicoder.me/problems/no/1265

消える奴は放置で良さそう
近い辺から見て行って片方が1ならそれを消す

"""

from sys import stdin

N = int(stdin.readline())

XY = []
for i in range(N):
    x,y = map(int,stdin.readline().split())
    XY.append((x,y))

lis = []
for i in range(N):
    x,y = XY[i]
    for j in range(i):
        X,Y = XY[j]
        lis.append(((x-X)**2+(y-Y)**2,i,j))

lis.sort()
able = [True] * N
ans = 0
for tmp,u,v in lis:
    if able[u] and able[v]:
        if u == 0:
            ans += 1
            able[v] = False
        elif v == 0:
            ans += 1
            able[u] = False
        else:
            able[v] = False
            able[u] = False
print (ans)