n=int(input())
x=[]
y=[]
for i in range(n):
    a,b=map(int,input().split());p=0
    for j,l in x:
        y.append(((a-j)**2+(b-l)**2,i,p))
        p+=1
    x.append((a,b))
y.sort()
ans=0;a=[0]*n
for i,j,l in y:
    if a[j] or a[l]:
        continue
    if not j or not l:
        ans+=1;a[max(j,l)]=1
    else:
        a[j]=1;a[l]=1
print(ans)