#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("trapez.in");
ofstream cout("trapez.out");
struct ura{
    int x,y;
} v[1001],vpant[1000001];
int modul(int a)
{
    if(a<0)
        return -a;
    return a;
}
ura fpant(ura a,ura b)
{
    ura rez;
    rez.x=modul(a.x-b.x);
    rez.y=modul(a.y-b.y);
    return rez;
}
bool cmp(ura a,ura b)
{
    return (a.x*b.y)<(a.y*b.x);
}
int main()
{
    int i,n,j,m=0,rez,l;
    cin>>n;
    for(i=1;i<=n;i++)
    {
        cin>>v[i].x>>v[i].y;
    }
    for(i=1;i<=n;i++)
    for(j=i+1;j<=n;j++)
    {
        m++;
        vpant[m]=fpant(v[i],v[j]);
    }
    sort(vpant+1,vpant+m+1,cmp);
    l=1;
    rez=0;
    for(i=2;i<=m;i++)
    {
        if(vpant[i].x==vpant[i-1].x && vpant[i].y==vpant[i-1].y)
            l++;
        else
        {
            rez+=l*(l-1)/2;
            l=1;
        }
    }
    cout<<rez;
    return 0;
}