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;
template <typename T>
string tostr(const T& t) {
  ostringstream os;
  os << t;
  return os.str();
}
struct Point {
 public:
  double x, y;
  Point() {}
  Point(double x, double y) : x(x), y(y) {}
  double atan2() const { return std::atan2(y, x); }
  double dot(Point p) { return x * p.x + y * p.y; }
  double cross(Point p) { return x * p.y - y * p.x; }
  bool operator<(const Point& b) const {
    const Point& a = (*this);
    if (a.x != b.x) return a.x < b.x;
    return a.y < b.y;
  }
  Point mid(Point p) { return Point((x + p.x) / 2.0, (y + p.y) / 2.0); }
};
struct compare_right {
  bool operator()(const Point& p1, const Point& p2) {
    if (p1.x == p2.x) return p1.y < p2.y;
    return p1.x < p2.x;
  };
};
vector<Point> pts;
int binsearch(Point& val) {
  int lo = 0;
  int hi = (int)pts.size();
  while (lo != hi) {
    int mid = lo + ((hi - lo) / 2);
    if (pts[mid] < val)
      lo = mid + 1;
    else
      hi = mid;
  }
  if (lo < 0 || lo >= (int)pts.size()) return -1;
  return fabs(pts[lo].x - val.x) <= 1e-9 && fabs(pts[lo].y - val.y) <= 1e-9
             ? lo
             : -1;
}
int main() {
  int n;
  cin >> n;
  for (int i = (int)(0); i <= (int)(n - 1); ++i) {
    Point p;
    cin >> p.x >> p.y;
    pts.push_back(p);
  }
  sort((pts).begin(), (pts).end());
  int ans = 0;
  for (int i = (int)(0); i <= (int)(n - 1); ++i) {
    for (int j = (int)(i + 1); j <= (int)(n - 1); ++j) {
      Point mid = pts[i].mid(pts[j]);
      int x = binsearch(mid);
      ans += x != -1;
    }
  }
  cout << ans << endl;
  return 0;
}
