#include <bits/stdc++.h>


#define MAX 1010
#define mp make_pair
#define ff first
#define ss second

typedef long long ll;
using namespace std;


struct myStruct
{
    ll x, y, mx, my;
    myStruct() {}
    myStruct(ll x, ll y, ll mx, ll my ) : x(x), y(y), mx(mx), my(my){};
    bool operator < (const myStruct &o) const
    {
        if ( x != o.x ) return x < o.x;
        if ( y != o.y ) return y < o.y;
        if ( mx != o.mx ) return mx < o.mx;
        return my < o.my;
    }
};

ll gcd(ll a, ll b)
{
    if ( b == 0ll) return a;
    return gcd(b, a%b);
}

int xs[MAX];
int ys[MAX];


int main()
{
    int n;
    cin>>n;
    map<pair<ll, ll>, ll> map1;
    map<myStruct, ll> map2;
    for( int i = 0; i < n; i++ )
    {
        cin>>xs[i]>>ys[i];
        xs[i] *= 2ll;
        ys[i] *= 2ll;
    }
    for( int i = 0; i < n; i++ )
    {
        for( int j = i+1; j < n; j++ )
        {
            ll cx = (xs[i]+xs[j])/2ll;
            ll cy = (ys[i]+ys[j])/2ll;
            ll dx = xs[i] - xs[j];
            ll dy = ys[i] - ys[j];
            ll myGcd = gcd(dx, dy);
            dx /= myGcd;
            dy /= myGcd;
            map1[mp(cx, cy)] = map1[mp(cx, cy)] + 1ll;
            map2[myStruct(cx, cy, dx, dy)] = map2[myStruct(cx, cy, dx, dy)] + 1ll;
        }
    }
    ll result = 0ll;
    for( auto v : map2 )
    {
        result += v.ss*(map1[mp(v.ff.x, v.ff.y)] - v.ss);
    }
    result /= 2ll;
    cout<<result<<"\n";
}