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;
short x[3000];
short y[3000];
short n;
void quickSort(short left, short right) {
  short i = left, j = right;
  short tmp;
  short pivot = x[(left + right) / 2];
  while (i <= j) {
    while (x[i] < pivot) i++;
    while (x[j] > pivot) j--;
    if (i <= j) {
      tmp = x[i];
      x[i] = x[j];
      x[j] = tmp;
      tmp = y[i];
      y[i] = y[j];
      y[j] = tmp;
      i++;
      j--;
    }
  }
  if (left < j) quickSort(left, j);
  if (i < right) quickSort(i, right);
}
short binarySearch(short xs, short ys) {
  static short b = 0;
  static short t = 0;
  static short min = 0;
  static short max = 0;
  min = 0;
  max = n + 1;
  b = -1;
  while (min <= max) {
    if (b == (min + max) / 2) return 0;
    b = (min + max) / 2;
    if ((2 * x[b] == xs)) {
      if (2 * y[b] == ys) {
        return 1;
      } else {
        t = b;
        while (2 * x[++b] == xs) {
          if (2 * y[b] == ys) return 1;
        }
        while (2 * x[--t] == xs) {
          if (2 * y[t] == ys) return 1;
        }
        return 0;
      }
    } else if (xs > 2 * x[b])
      min = b;
    else
      max = b;
  }
  return 0;
}
int main() {
  cin >> n;
  for (short i = 0; i < n; i++) cin >> x[i] >> y[i];
  quickSort(0, n - 1);
  short answer = 0;
  for (short a = 0; a < n - 1; a++) {
    for (short c = a + 1; c < n; c++) {
      answer += binarySearch(x[a] + x[c], y[a] + y[c]);
    }
  }
  cout << answer << endl;
  return 0;
}
