n=int(input())
X=[0]*n
Y=[0]*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())

    X[i]=x
    Y[i]=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,yj=X[i],Y[i],X[j],Y[j]
        dis[cnt][0]=(xi-xj)**2+(yi-yj)**2
        dis[cnt][1]=i
        dis[cnt][2]=j
        cnt+=1
dis.sort()
erase=set()
for i in range(len(dis)):
    p,q=dis[i][1],dis[i][2]
    if p==0:
        if not q in erase:
            ans+=1
            erase.add(q)
    else:
        if not p in erase and not q in erase:
            erase.add(p)
            erase.add(q)

print(ans)