D = []
for dx in range(-20, 21):
    for dy in range(-20, 21):
        dd = dx * dx + dy * dy
        if dd < 400:
            D.append((dx, dy))

def f(x, y):
    return x * 50000 + y

se = set()
n = int(input())
for _ in range(n):
    x, y = map(int, input().split())
    ok = True
    for dx, dy in D:
        if f(x + dx, y + dy) in se:
            ok = False
            break
    if ok:
        se.add(f(x, y))

print(len(se))