import sys

from collections import *

int1 = lambda x: int(x)-1
p2D = lambda x: print(*x, sep="\n")
def II(): return int(sys.stdin.readline())
def SI(): return sys.stdin.readline()[:-1]
def MI(): return map(int, sys.stdin.readline().split())
def MI1(): return map(int1, sys.stdin.readline().split())
def MF(): return map(float, sys.stdin.readline().split())
def LI(): return list(map(int, sys.stdin.readline().split()))
def LI1(): return list(map(int1, sys.stdin.readline().split()))
def LF(): return list(map(float, sys.stdin.readline().split()))
def LLI(rows_number): return [LI() for _ in range(rows_number)]
dij = [(0, 1), (1, 0), (0, -1), (-1, 0)]

def main():
    def crash(x0, y0):
        i0, j0 = x0//20, y0//20
        for i in range(i0-1, i0+2):
            for j in range(j0-1, j0+2):
                if (i, j) not in p: continue
                for x, y in p[i, j]:
                    if (x-x0)**2+(y-y0)**2 < 400:
                        return True
        return False

    n = II()
    p = defaultdict(list)
    ans = 0
    for _ in range(n):
        x, y = MI()
        if crash(x, y): continue
        p[x//20, y//20].append((x, y))
        ans += 1
    print(ans)

main()