#include<bits/stdc++.h>
using namespace std;
template<typename T>
T gcd(T a, T b){return b==0?a:gcd(b,a%b);}
int N,X[1010],Y[1010];
int main()
{
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    cin>>N;
    for(int i=0;i<N;i++)cin>>X[i]>>Y[i];
    map<tuple<int,int,int,int>,int>mp;
    long ans=0;
    for(int i=0;i<N;i++)for(int j=0;j<i;j++)
    {
        int mx=X[i]+X[j],my=Y[i]+Y[j];
        int dx=X[i]-X[j],dy=Y[i]-Y[j];
        int g=gcd(abs(dx),abs(dy));
        dx/=g,dy/=g;
        if(dx<0)dx=-dx,dy=-dy;
        ans+=mp[make_tuple(mx,my,-dy,dx)];
        ans+=mp[make_tuple(mx,my,dy,-dx)];
        mp[make_tuple(mx,my,dx,dy)]++;
    }
    cout<<ans<<endl;
}