#include <bits/stdc++.h>   using namespace std;   const int N = 2005;   bool f[N][N];   int x[3005], y[3005];   int main() {     int n;     cin >> n;     for (int i = 1; i <= n; i++) {       cin >> x[i] >> y[i];       f[x[i] + 1000][y[i] + 1000] = true;     }     int ans = 0;     for (int i = 1; i <= n; i++) {       for (int j = i + 1; j <= n; j++) {         if ((x[i] + x[j]) % 2 != 0 || (y[i] + y[j]) % 2 != 0) continue;         int x_md = (x[i] + x[j]) / 2;         int y_md = (y[i] + y[j]) / 2;         if (f[x_md + 1000][y_md + 1000] == 1) ans++;       }     }     cout << ans << endl;   }   