def dist(p,q):
    a,b=p[0]-q[0],p[1]-q[1]
    return a**2+b**2
    
N=int(input())
point=[tuple(map(int,input().split())) for _ in range(N)]
G=[]

isv=[True]*N

for i in range(N):
    for j in range(i+1,N):
        G.append((dist(point[i],point[j]),i,j))
G.sort()
res=0
for d,i,j in G:
    if i==0:
        if isv[j]:
            res+=1
            isv[j]=False
    if j==0:
        if isv[i]:
            res+=1
            isv[i]=False
    else:
        if not isv[i] or not isv[j]:
            continue
        isv[i]=False
        isv[j]=False
print(res)