d = [[[] for _ in range(1002)] for _ in range(1002)]
n = int(input())
ans = 0
for _ in range(n):
    x,y = map(int,input().split())
    px,py = x//20, y//20
    ok = 1
    for i in range(-1,2):
        for j in range(-1,2):
            if px+i < 0 or py+j < 0: continue
            for v,w in d[px+i][py+j]:
                if (x-v)**2 + (y-w)**2 < 400:
                    ok = 0
    if ok:
        ans += 1
        d[px][py].append((x,y))

print(ans)