#include <bits/stdc++.h>   using namespace std;   pair<double, double> midpoint(double x1, double y1, double x2, double y2) {     return {(x1 + x2) / 2, (y1 + y2) / 2};   }   int main() {     ios_base::sync_with_stdio(0);     cin.tie(0);     cout.tie(0);     int n;     cin >> n;     map<pair<double, double>, int> mp;     pair<double, double> pr[n + 5];     for (int i = 0; i < n; i++) {       cin >> pr[i].first >> pr[i].second;       mp[pr[i]]++;     }     int ans = 0;     for (int i = 0; i < n; i++) {       for (int j = i + 1; j < n; j++) {         if (mp.find(midpoint(pr[i].first, pr[i].second, pr[j].first,                              pr[j].second)) != mp.end())           ans++;       }     }     cout << ans;     return 0;   }   