10
-2 1
2 -2
-1 -2
0 0
2 -1
0 -2
2 2
0 2
-1 -1
1 -2
 40
-8 24
2 -1
1 -18
72 -70
5 -4
-308 436
-19 40
36 -35
-178 265
-1 2
-7 30
-1 0
3 -2
200 -285
17 -16
-35 74
0 -4
-86 106
-1 4
-7 6
0 1
-5 4
-2 3
6 -5
-4 5
181 -262
76 -118
0 0
-7 18
-58 104
-5 6
-6 12
-3 4
1 0
11 -10
-86 130
-3 6
153 -236
-183 270
-33 64
 5
0 -1
0 -2
0 -3
0 -4
0 -5
 10
0 1
-1 -1
1 1
-1 0
1 -1
-2 -1
-2 2
-2 0
0 -2
0 -1
 20
-1 18
-2 5
-5 4
2 -33
9 -18
0 0
11 -22
2 0
-1 2
-4 41
1 6
1 -2
6 -12
0 1
-3 6
3 -6
3 -8
-1 4
2 -5
1 0
 10
2 1
-1 0
-2 -1
-1 1
0 2
2 -2
0 0
-2 -2
0 -2
-2 1
 20
-3 -3
0 4
-3 1
1 1
-1 2
-4 4
3 -1
-3 0
0 2
4 0
2 3
2 4
4 -3
-4 3
-1 1
1 3
-2 4
1 -2
1 -1
3 0
 3
0 0
0 -1
0 1
 10
2 1
-1 1
0 0
-3 1
-2 -3
-1 -2
-1 -1
1 2
3 -2
0 -2
 3
3 3
1 2
1 1
 4
0 0
1 0
2 0
3 0
 9
1 1
1 0
0 1
0 0
-1 0
-1 1
-1 -1
1 -1
0 -1
 7
1 1
-1 -1
1 0
0 1
-1 0
0 -1
0 0

4
 57
 4
 5
 21
 4
 10
 1
 1
 0
 2
 8
 3

from sys import maxsize, stdout, stdin,stderr
mod = int(1e9 + 7)
import sys
def I(): return int(stdin.readline())
def lint(): return [int(x) for x in stdin.readline().split()]
def S(): return input().strip()
def grid(r, c): return [lint() for i in range(r)]
from collections import defaultdict, Counter
import math
import heapq
from heapq import heappop , heappush
import bisect
from itertools import groupby
def gcd(a,b): 
    while b:
        a %= b
        tmp = a
        a = b
        b = tmp
    
    return a
 
def lcm(a,b): 
    return a  / gcd(a, b) * b
 
def check_prime(n):
    for i in range(2, int(n ** (1 / 2)) + 1):
        if not n % i:
            return False
    return True
def Bs(a, x):
    i=0
    j=0
    left = 1
    right = k
    flag=False
    while left<right:
        
        mi = (left+right)//2
        #print(smi,a[mi],x)
        
        if a[mi]<=x:
            left = mi+1
            i+=1
            
        else:
 
            right = mi
            j+=1
        #print(left,right,"----")
    #print(i-1,j)
    if left>0 and a[left-1]==x:
        return i-1, j
    else:
        return -1, -1
def nCr(n, r):
 
    return (fact(n) // (fact(r)
                * fact(n - r)))
 
# Returns factorial of n
def fact(n):
 
    res = 1
     
    for i in range(2, n+1):
        res = res * i
         
    return res
def primefactors(n):
    num=0
    
    while n % 2 == 0:
        num+=1
        n = n / 2
    
    for i in range(3,int(math.sqrt(n))+1,2):
         
    
        while n % i== 0:
            num+=1
            n = n // i
               
    
    if n > 2:
        num+=1
    return num
'''
def iter_ds(src):
    store=[src]
    while len(store):
        tmp=store.pop()
        if not vis[tmp]:
            vis[tmp]=True
            for j in ar[tmp]:
                store.append(j)
'''
def ask(a):
    print('? {}'.format(a),flush=True)
    n=lint()
    
    return n

def bstemp(n,k):
    l=1
    r=n+1
    while l<r:
        mid=(l+r)//2
        if (mid*(mid+1)*5)//2+k<=4*60:
            
            l=mid+1
            
        else:
            r=mid
      
    return l
 
def dfs(i,p):
    
    a,tmp=0,0
    for j in d[i]:
        if j!=p:
            a+=1
            tmp+=dfs(j,i)
    
    if a==0:
        return 0
    
    return tmp/a + 1 
def primeFactors(n):
    l=[]
    
    while n % 2 == 0:
        l.append(2)
        n = n // 2
         

    if n > 2:
        l.append(n)
    return l


n = I()
d=set()
s=[]
for _ in range(n):
    x,y=lint()
    s.append([x,y])
    d.add((x,y))
ans=0
for i in range(n):
    for j in range(i+1,n):
        x=s[i][0]+s[j][0]
        y=s[i][1]+s[j][1]
        if not (x%2 or y%2):
            
            if (x//2,y//2) in d:
                
                ans+=1
print(ans)






