size=50
def dist(ax,ay,bx,by):
    return (ax-bx)**2+(ay-by)**2
def check(x,y):
    for dy in xrange(-1,2):
        for dx in xrange(-1,2):
            bx,by=x/size+dx,y/size+dy
            if 0<=bx<20000/size+1 and 0<=by<20000/size+1:
                for cx,cy in block[by][bx]:
                    if dist(x,y,cx,cy)<400:
                        return False
    return True
N=int(raw_input())
block=[[[] for i in xrange(20000/size+1)] for j in xrange(20000/size+1)]
ans=0
for loop in xrange(N):
    x,y=map(int,raw_input().split())
    if check(x,y):
        ans+=1
        block[y/size][x/size].append((x,y))
print ans