import sys

def dist(P,Q):
    a,b=P[0]-Q[0],P[1]-Q[1]
    return a*a+b*b

def main():
    N=int(input())
    P=[0]*N

    for i in range(N):
        P[i]=tuple(map(int,input().split()))

    Q=[0]*(N*(N-1)//2)
    k=0
    for i in range(N):
        for j in range(i+1,N):
            Q[k]=(dist(P[i],P[j]),j,i)
            k+=1

    Q.sort()
    Flag=[True for _ in range(N)]

    X=0
    for (_,j,i) in Q:
        if not(Flag[i] and Flag[j]):
            continue

        Flag[j]=False
        if i!=0:
            Flag[i]=False
        else:
            X+=1
    print(X)

main()