import sys
readline = sys.stdin.readline


def f(a, b):
    return (X[a] - X[b])**2 + (Y[a] - Y[b])**2

N = int(readline())
X, Y = [0] * N, [0] * N
for i in range(N):
    X[i], Y[i] = map(int, readline().split())
L = []
for i in range(N):
    for j in range(i + 1, N):
        L.append((f(i, j), i, j))
        
L.sort()
S = [0] * N
ans = 0
for _, i, j in L:
    if i == 0:
        if S[j]:
            continue
        else:
            ans += 1
            S[j] = 1
    else:
        if S[i] == 0  and S[j] == 0:
            S[i] = 1
            S[j] = 1
print(ans)