N=int(raw_input())
segs=[[[] for i in range(510)] for j in range(510)]

ans=0
for i in range(N):
    x,y=map(int,raw_input().split())
    xi,yj=(x/40)+1,(y/40+1)
    ok=True
    for dx in (-1,0,1):
        for dy in (-1,0,1):
            for (p,q) in segs[xi+dx][yj+dy]:
                if (p-x)*(p-x)+(q-y)*(q-y)<400:
                    ok=False
                    break
    if ok:
        ans+=1
        segs[xi][yj].append((x,y))
print ans