#include<iostream>
#include<map>
#include<vector>
#include<cassert>
using namespace std;
int gcd(int a,int b)
{
	while(b)
	{
		int t=a%b;
		a=b;
		b=t;
	}
	return a;
}
int N;
int X[1000],Y[1000];
map<pair<int,int>,vector<pair<int,int> > >mp1,mp2;
int main()
{
	ios::sync_with_stdio(false);
	cin.tie(nullptr);
	cin>>N;
	for(int i=0;i<N;i++)cin>>X[i]>>Y[i];
	for(int i=0;i<N;i++)for(int j=i+1;j<N;j++)
	{
		int dx=X[j]-X[i],dy=Y[j]-Y[i];
		int g=gcd(dx,dy);
		dx/=g,dy/=g;
		if(dx!=0)
		{
			if(dx<0)dx=-dx,dy=-dy;
			if(dy<0)mp1[make_pair(dx,dy)].emplace_back(X[i]+X[j],Y[i]+Y[j]);
			else mp2[make_pair(dy,-dx)].emplace_back(X[i]+X[j],Y[i]+Y[j]);
		}
		else mp1[make_pair(0,-1)].emplace_back(X[i]+X[j],Y[i]+Y[j]);
	}
	long ans=0;
	for(auto p:mp1)
	{
		auto it=mp2.find(p.first);
		if(it==mp2.end())continue;
		map<pair<int,int>,int>cnt;
		for(auto q:p.second)cnt[q]++;
		for(auto q:it->second)ans+=cnt[q];
	}
	cout<<ans<<endl;
}