#include <bits/stdc++.h>   using namespace std;   int main() {     map<pair<int, int>, int> dat;     vector<pair<int, int> > p;     int np;     cin >> np;     int res = 0;     while (np--) {       int x, y;       cin >> x >> y;       p.push_back(make_pair(x, y));       dat[make_pair(x, y)] = 1;     }     int sz = p.size();     for (int i = 0; i < sz; i++)       for (int j = i + 1; j < sz; j++) {         double x = p[i].first + p[j].first;         double y = p[i].second + p[j].second;         x /= 2.0;         y /= 2.0;         pair<int, int> tmp;         if (fabs(x - int(x)) < 1e-9 && fabs(y - int(y)) < 1e-9) {           tmp = make_pair(int(x), int(y));           if (dat.find(tmp) != dat.end()) res++;         }       }     cout << res << endl;   }   