N =int(input())
pa=[tuple(int(a) for a in input().split()) for i in range(N)]
pb=[]
for i,(xi,yi) in enumerate(pa[:-1]):
    for j in range(i+1,N):
        xj,yj=pa[j]
        r=(xi-xj)**2+(yi-yj)**2
        pb.append((r,i,j))
pb.sort()
pc=[0]*N
cn=0
for r,i,j in pb:
    if pc[i] or pc[j]: continue
    pc[j]=1
    if i>0: pc[i]=1
    else:   cn+=1
print(cn)