10
-2 1
2 -2
-1 -2
0 0
2 -1
0 -2
2 2
0 2
-1 -1
1 -2
 40
-8 24
2 -1
1 -18
72 -70
5 -4
-308 436
-19 40
36 -35
-178 265
-1 2
-7 30
-1 0
3 -2
200 -285
17 -16
-35 74
0 -4
-86 106
-1 4
-7 6
0 1
-5 4
-2 3
6 -5
-4 5
181 -262
76 -118
0 0
-7 18
-58 104
-5 6
-6 12
-3 4
1 0
11 -10
-86 130
-3 6
153 -236
-183 270
-33 64
 5
0 -1
0 -2
0 -3
0 -4
0 -5
 10
0 1
-1 -1
1 1
-1 0
1 -1
-2 -1
-2 2
-2 0
0 -2
0 -1
 20
-1 18
-2 5
-5 4
2 -33
9 -18
0 0
11 -22
2 0
-1 2
-4 41
1 6
1 -2
6 -12
0 1
-3 6
3 -6
3 -8
-1 4
2 -5
1 0
 10
2 1
-1 0
-2 -1
-1 1
0 2
2 -2
0 0
-2 -2
0 -2
-2 1
 20
-3 -3
0 4
-3 1
1 1
-1 2
-4 4
3 -1
-3 0
0 2
4 0
2 3
2 4
4 -3
-4 3
-1 1
1 3
-2 4
1 -2
1 -1
3 0
 3
0 0
0 -1
0 1
 10
2 1
-1 1
0 0
-3 1
-2 -3
-1 -2
-1 -1
1 2
3 -2
0 -2
 3
3 3
1 2
1 1
 4
0 0
1 0
2 0
3 0
 9
1 1
1 0
0 1
0 0
-1 0
-1 1
-1 -1
1 -1
0 -1
 7
1 1
-1 -1
1 0
0 1
-1 0
0 -1
0 0

4
 57
 4
 5
 21
 4
 10
 1
 1
 0
 2
 8
 3

#include <bits/stdc++.h>
using namespace std;
bool vec[2001][2001];
pair<int, int> func(pair<int, int> &p1, pair<int, int> p2) {
  if ((p1.first + p2.first) % 2 == 0 && (p1.second + p2.second) % 2 == 0)
    return make_pair((p1.first + p2.first) / 2 + 1000,
                     (p1.second + p2.second) / 2 + 1000);
  return make_pair(-1, -1);
}
bool check(pair<double, double> &p1, pair<int, int> &p2) {
  return p1.first == (double)p2.first && p1.second == (double)p2.second;
}
int main() {
  int n;
  cin >> n;
  vector<pair<int, int> > v(n + 1);
  for (int i = 1; i <= n; i++) {
    cin >> v[i].first >> v[i].second;
    vec[v[i].first + 1000][v[i].second + 1000] = true;
  }
  int count = 0;
  pair<int, int> p;
  for (int i = 1; i <= n; i++) {
    for (int j = i + 1; j <= n; j++) {
      p = func(v[i], v[j]);
      if (p.first != -1 && p.second != -1 && vec[p.first][p.second]) {
        count++;
      }
    }
  }
  cout << count;
  return 0;
}
