#include<bits/stdc++.h>
using namespace std;

map<pair<long long, long long>, vector<pair<long long, long long>>> mp;

int main() {
    int n;
    cin >> n;
    vector<long long> x(n);
    vector<long long> y(n);
    for (int i = 0; i < n; i++) {
        cin >> x[i] >> y[i];
    }
    int ans = 0;
    for (int i = 0; i < n; i++) {
        for (int j = i+1; j < n; j++) {
            long long tx = x[i]-x[j];
            long long ty = y[i]-y[j];
            long long nx = x[i]+x[j];
            long long ny = y[i]+y[j];
            if (mp.find({nx, ny}) != mp.end()) {
                for (auto [x, y]: mp[{nx, ny}]) {
                    if (tx*x + ty*y == 0) ans++;
                }
            } 
            mp[{nx, ny}].push_back({tx, ty});
        }
    }
    cout << ans << endl;
}