from collections import deque
from operator import itemgetter

import sys
input=sys.stdin.readline

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

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

    dist=[0]*(N*(N-1)//2)
    I=[0]*(N*(N-1)//2)
    J=[0]*(N*(N-1)//2)

    k=0
    for i in range(N):
        for j in range(i+1,N):
            a,b=P[i][0]-P[j][0],P[i][1]-P[j][1]
            I[k]=i; J[k]=j; dist[k]=a*a+b*b
            k+=1

    A=sorted(range(N*(N-1)//2), key=lambda k:dist[k])
    Flag=[1]*N

    X=0
    for k in A:
        i=I[k]; j=J[k]
        if not(Flag[i] and Flag[j]):
            continue

        Flag[j]=0
        if i!=0:
            Flag[i]=0
        else:
            X+=1
    return X

if __name__=="__main__":
    print(main())