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;
int main() {
  int n;
  cin >> n;
  int a[n][2], br = 0;
  for (int i = 0; i < n; i++) cin >> a[i][0] >> a[i][1];
  int p[2];
  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++) {
      if (a[j][0] < a[i][0]) {
        p[0] = a[i][0];
        p[1] = a[i][1];
        a[i][0] = a[j][0];
        a[i][1] = a[j][1];
        a[j][0] = p[0];
        a[j][1] = p[1];
      } else if ((a[j][0] == a[i][0]) && (a[j][1] < a[i][1])) {
        p[0] = a[i][0];
        p[1] = a[i][1];
        a[i][0] = a[j][0];
        a[i][1] = a[j][1];
        a[j][0] = p[0];
        a[j][1] = p[1];
      }
    }
  int donjagranica = 0, gornjagranica = n - 1, sredina;
  int donjagranica2, gornjagranica2, sredina2;
  double g[2];
  for (int i = 0; i < n; i++)
    for (int j = i + 1; j < n; j++) {
      g[0] = (a[i][0] + a[j][0]) / 2.0;
      g[1] = (a[i][1] + a[j][1]) / 2.0;
      while (a[donjagranica][0] != a[gornjagranica][0]) {
        sredina = (donjagranica + gornjagranica) / 2;
        if (a[sredina][0] >= g[0])
          gornjagranica = sredina;
        else
          donjagranica = sredina + 1;
      }
      while (a[gornjagranica][0] == a[gornjagranica + 1][0]) {
        gornjagranica++;
      }
      while (a[donjagranica][0] == a[donjagranica - 1][0]) {
        donjagranica--;
      }
      donjagranica2 = donjagranica;
      gornjagranica2 = gornjagranica;
      while (donjagranica2 < gornjagranica2) {
        sredina2 = (donjagranica2 + gornjagranica2) / 2;
        if (a[sredina2][1] >= g[1])
          gornjagranica2 = sredina2;
        else
          donjagranica2 = sredina2 + 1;
      }
      if ((a[donjagranica2][0] == g[0]) && (a[donjagranica2][1] == g[1])) br++;
      gornjagranica = n - 1;
      donjagranica = 0;
    }
  cout << br;
  return 0;
}
