N=int(raw_input())
S=set([])
ans=0
for i in range(N):
    x,y=map(int,raw_input().split())
    if (x,y) not in S:
        ans+=1
        for i in range(-20,21):
            for j in range(-20,21):
                if i*i+j*j<20*20:
                    S.add((x+i,y+j))
print ans