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;
void razbor(int, int, int);
void ssort(int, int);
int x[3000], y[3000], rez = 0;
int main() {
  int n, i, j, l, r, m, mx, my;
  cin >> n;
  for (i = 0; i < n; i++) cin >> x[i] >> y[i];
  ssort(0, n);
  for (i = 0; i < n - 1; i++) {
    for (j = i + 1; j < n; j++) {
      if ((x[i] - x[j]) % 2 or (y[i] - y[j]) % 2) continue;
      mx = (x[i] + x[j]) / 2;
      my = (y[i] + y[j]) / 2;
      l = i + 1;
      r = j;
      while (r - l > 1) {
        m = (l + r) / 2;
        if (x[m] > mx)
          r = m;
        else if (x[m] == mx)
          if (y[m] > my)
            r = m;
          else
            l = m;
        else
          l = m;
      }
      if (x[l] == mx and y[l] == my) rez++;
    }
  }
  cout << rez;
}
void razbor(int a, int m, int b) {
  int x1[3000], y1[3000];
  int i = a, j = m;
  for (int h = a; h < b; h++) {
    if ((x[i] > x[j] or i == m) and j != b) {
      x1[h] = x[j];
      y1[h] = y[j];
      j++;
    } else if (x[i] == x[j] and i != m and j != b) {
      if (y[i] > y[j]) {
        x1[h] = x[j];
        y1[h] = y[j];
        j++;
      } else {
        x1[h] = x[i];
        y1[h] = y[i];
        i++;
      }
    } else {
      x1[h] = x[i];
      y1[h] = y[i];
      i++;
    }
  }
  for (int h = a; h < b; h++) {
    x[h] = x1[h];
    y[h] = y1[h];
  }
}
void ssort(int a, int b) {
  if (b - a > 1) {
    int m = (a + b) / 2;
    ssort(a, m);
    ssort(m, b);
    razbor(a, m, b);
  }
}
