from heapq import heappush, heappop, heapify
from collections import defaultdict, deque,Counter
from math import ceil, floor, sqrt, factorial,gcd,cos,sin,pi
from itertools import permutations, combinations,product
from bisect import bisect_left, bisect_right
from copy import deepcopy
from fractions import Fraction
from random import randint
import sys
from functools import cache,lru_cache #@lru_cache(maxsize=None)
from time import time
#from sortedcontainers import SortedList # type: ignore
#sys.setrecursionlimit(10**6)
vector1 = [[0, -1], [1, 0], [0, 1], [-1, 0]]
vector2 = [[0, 1], [1, 0], [-1, 0], [0, -1],
           [1,-1], [-1, 1], [1, 1], [-1, -1]]
alphabet = "abcdefghijklmnopqrstuvwxyz"


def make_divisors(n):
    lower_divisors, upper_divisors = [], []
    i = 1
    while i * i <= n:
        if n % i == 0:
            lower_divisors.append(i)
            if i != n // i:
                upper_divisors.append(n//i)
        i += 1
    return lower_divisors + upper_divisors[::-1]


def main():
    
    N = int(input())
    p = [list(map(int,input().split())) for _ in range(N)]
    d = defaultdict(list)
    ans = 0
    for i in range(N):
        for j in range(i+1,N):
            cx = p[i][0] + p[j][0]
            cy = p[i][1] + p[j][1]
            vx = p[i][0] - p[j][0]
            vy = p[i][1] - p[j][1]
            for ux,uy in d[(cx,cy)]:
                if vx * ux + vy*uy == 0:
                    ans += 1
            d[(cx,cy)].append((vx,vy))
    print(ans)
    

if __name__ == '__main__':
    main()