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