N = int(input())

d = dict()
for _ in range(N):
    x,y = map(int,input().split())
    s = x // 10
    t = y // 10
    flag = True
    for i in range(-2,3):
        for j in range(-2,3):
            if (s+i,t+j) in d:
                u,v = d[(s+i,t+j)]
                if (u-x) ** 2 + (v - y) ** 2 < 400:
                    flag = False
    if flag:
        d[(s,t)] = (x,y)
print(len(d))
#print(d)