# 全点対の距離、昇順で並べる
# popしてなければ両方pop
# 1とpopしていないbaloonであれば取り除く=pop

N = int(input())
XY = []
for i in range(N):
    x, y = map(int, input().split())
    XY.append([x, y])
    
d_list = []
for i in range(N):
    for j in range(i+1, N):
        d = (XY[i][0]-XY[j][0])**2 + (XY[i][1]-XY[j][1])**2
        d_list.append((d, i, j))
d_list.sort()
        
pop = [0]*N
ans = 0
for d, i, j in d_list:
    if i == 0:
        if pop[j] == 0:
            pop[j] = 1
            ans += 1
    else:
        if pop[i] == 0 and pop[j] == 0:
            pop[i] = 1
            pop[j] = 1

print(ans)