#include<bits/stdc++.h>
using namespace std;
#include <atcoder/all>
using namespace atcoder;
using mint=modint998244353; //1000000007;
using ll=long long;
using pp=pair<ll,ll>;
#define sr string 
#define vc vector
#define fi first
#define se second
#define rep(i,n) for(int i=0;i<(int)n;i++)
#define pb push_back
#define all(v) v.begin(),v.end()
#define pque priority_queue
#define bpc(a) __builtin_popcount(a)
int main(){
  int n;cin>>n;
  vc<pp>v(n); rep(i,n)cin>>v[i].fi>>v[i].se;
  map<pair<pp,pp>,int>m;
  rep(i,n)rep(j,i){
    auto [a,b]=v[i]; 
    auto [c,d]=v[j];
    ll dx=a-c,dy=b-d;
    if(dx<0)dx=-dx,dy=-dy;
    ll g=gcd(dx,dy);
   
    dx/=g,dy/=g;
     if(dx==0)dy=1;
    m[{{dx,dy},{a+c,b+d}}]++;
  }
  ll ans=0;
  rep(i,n)rep(j,i){
    auto [a,b]=v[i]; 
    auto [c,d]=v[j];
    ll dx=a-c,dy=b-d;
    swap(dx,dy);
    dx=-dx;
    if(dx<0)dx=-dx,dy=-dy;
    ll g=gcd(dx,dy);
    dx/=g,dy/=g;
     if(dx==0)dy=1;
    ans+=m[{{dx,dy},{a+c,b+d}}];
  }
  ans/=2;
  cout<<ans;
}