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;
struct node {
  double x, y;
} p[3007];
int n;
int cmp(node a, node b) {
  if (a.x != b.x)
    return a.x < b.x;
  else
    return a.y < b.y;
}
bool bsearch(node t) {
  int l = 0, r = n;
  while (l < r) {
    int m = (l + r) / 2;
    if (p[m].x == t.x && p[m].y == t.y)
      return true;
    else if (p[m].x > t.x)
      r = m - 1;
    else if (p[m].x == t.x && p[m].y > t.y)
      r = m - 1;
    else if (p[m].x == t.x && p[m].y < t.y)
      l = m + 1;
    else if (p[m].x < t.x)
      l = m + 1;
  }
  return false;
}
int main() {
  int i, j;
  node t;
  while (scanf("%d", &n) != EOF) {
    int ct = 0;
    for (i = 0; i < n; ++i) scanf("%lf%lf", &p[i].x, &p[i].y);
    sort(p, p + n, cmp);
    for (i = 0; i < n - 1; ++i) {
      for (j = i + 1; j < n; ++j) {
        t.x = (p[i].x + p[j].x) / 2;
        t.y = (p[i].y + p[j].y) / 2;
        if (t.x != (int)t.x) continue;
        if (t.y != (int)t.y) continue;
        if (bsearch(t)) ct++;
      }
    }
    printf("%d\n", ct);
  }
  return 0;
}
