#include <bits/stdc++.h>
using namespace std;
using ll=long long;
using pll=pair<ll,ll>;
using tll=tuple<ll,ll,ll>;
using ld=long double;
const ll INF=(1ll<<60);
#define rep(i,n) for (ll i=0;i<(ll)(n);i++)
#define all(v) v.begin(),v.end()
template<class T> inline bool chmin(T &a,T b){
    if(a>b){
        a=b;
        return true;
    }
    return false;
}
template<class T> inline bool chmax(T &a,T b){
    if(a<b){
        a=b;
        return true;
    }
    return false;
}
ll x[1000],y[1000];
int main(){
    ios::sync_with_stdio(false);
    cin.tie(nullptr);
    map<pll,vector<pll>> mp;
    ll n;
    cin >> n;
    rep(i,n) cin >> x[i] >> y[i];
    rep(i,n){
        rep(j,i){
            mp[{x[i]+x[j],y[i]+y[j]}].emplace_back(x[j]-x[i],y[j]-y[i]);
        }
    }
    ll ans=0;
    for(auto [k,v]:mp){
        map<pll,ll> cnt;
        for(auto p:v) cnt[p]++;
        for(auto [p,c]:cnt){
            for(auto [q,d]:cnt){
                auto [ax,ay]=p;
                auto [bx,by]=q;
                if(ax*bx+ay*by==0) ans+=c*d;
            }
        }
    }
    ans/=2;
    cout << ans << '\n';
}