n=int(input())
xy=[[0,0] for i in range(n)]
import sys
input=sys.stdin.readline #文字列入力はするな！

for i in range(n):
    x,y=map(int,input().split())

    xy[i][0]=x
    xy[i][1]=y
ans=0

dis=[[0,0,0] for i in range(n*(n-1)//2)]
cnt=0
for i in range(n-1):
    for j in range(i+1,n):
        xi,yi,xj,yj0=xy[i][0],xy[i][1],xy[j][0],xy[j][1]
        dis[cnt][0]=(xi-xj)**2+(xi-xj)**2
        dis[cnt][1]=i
        dis[cnt][2]=j
        cnt+=1
dis.sort()
erase=[0]*(n)
for i in range(len(dis)):
    p,q=dis[i][1],dis[i][2]
    if p==0:
        if erase[q]==0:
            ans+=1
            erase[q]=1
    else:
        if erase[p]==erase[q]==0:
            erase[p] = erase[q]=1

print(ans)