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)