from collections import deque

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()))

    Q=[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]
            Q[k]=(a*a+b*b,j,i)
            k+=1

    Q.sort(key=lambda x:x[0])
    Q=deque(Q)
    Flag=[True for _ in range(N)]

    X=0
    while Q:
        _,j,i=Q.popleft()
        if not(Flag[i] and Flag[j]):
            continue

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

if __name__=="__main__":
    main()