def distance(X, Y):
    return abs(X[0] - Y[0])**2 + abs(X[1] - Y[1])**2

n = int(input())
f = list(map(int, input().split()))
xy = [list(map(int, input().split())) for _ in range(n-1)]
d = []
for i in range(n-1):
    d.append((distance(f, xy[i]), xy[i]))
d.sort()
for i in range(n-1):
    xy[i] = d[i][1]

delete = set()
exploded = set()

for i in range(n-1):
    if i in exploded:
        continue
    fd = distance(f, xy[i])
    MIN = fd
    minIdx = -1
    for g in range(n-1):
        if g in delete or g in exploded or g == i:
            continue
        d = distance(xy[i], xy[g])
        if MIN > d:
            MIN = d
            minIdx = g

    if minIdx == -1:
        delete.add(i)
    else:
        exploded.add(i)
        exploded.add(minIdx)

print(len(delete))