#include <fstream>
#include <map>
#include <algorithm>
#define nmax 1000
#define inf 1000000

using namespace std;

struct pct
{
    int x, y;
};
bool cmp (pct a, pct b)
{
    if (a.x == b.x)
        return a.y < b.y;
    return a.x < b.x;
}
struct panta
{
    int numa, numi;
    bool operator< (const panta& a)const
    {
        if (numa == a.numa)
            return numi < a.numi;
        return numa < a.numa;
    }
};
panta pantify (pct a, pct b)
{
    if (b.x - a.x == 0)
        return {inf, inf};
    int gcd = __gcd (b.y - a.y, b.x - a.x);
    panta x = { (b.y - a.y) / gcd, (b.x - a.x) / gcd};
    if (x.numa < 0 && x.numi < 0)
        x.numa *= -1, x.numi *= -1;
    else if (x.numi < 0)
        x.numa *= -1, x.numi *= -1;
    return x;
}
const double eps = 1e-6, cons = 1.0000000;
pct v[nmax + 1];
map<panta, int> f;
map<panta, int>::iterator it;

int main()
{
    ifstream cin ("trapez.in");
    ofstream cout ("trapez.out");
    int n, i, j;
    long long tot = 0;
    cin >> n;
    for (i = 1; i <= n; i++)
        cin >> v[i].x >> v[i].y;
    sort (v + 1, v + n + 1, cmp);
    for (i = 1; i <= n; i++)
        for (j = i + 1; j <= n; j++)
            f[pantify (v[i], v[j])]++;
    for (it = f.begin(); it != f.end(); it++)
        tot += (it->second) * (it->second - 1) / 2;
    cout << tot;
    return 0;
}