import sys
input = sys.stdin.readline

n = int(input())
X = [0] * n
Y = [0] * n
for i in range(n):
    X[i], Y[i] = map(int, input().split())
dist = []
for i in range(n):
    for j in range(i + 1, n):
        dx = X[j] - X[i]
        dy = Y[j] - Y[i]
        dist.append((dx ** 2 + dy ** 2, i, j))
        
dist.sort()
used = [False] * n
ans = 0
for _, i, j in dist:
    if i == 0:
        if not used[j]:
            ans += 1
            used[j] = True
    elif not used[i] and not used[j]:
        used[i] = used[j] = True
    else:
        pass
print(ans)