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 n, m;
struct TPoint {
  int x, y;
} tp[10000];
bool cmp(TPoint a, TPoint b) { return a.x < b.x || (a.x == b.x && a.y < b.y); }
bool find(TPoint t) {
  int l = 0, r = n - 1, mid;
  while (l <= r) {
    mid = (l + r) >> 1;
    if (tp[mid].x == t.x && tp[mid].y == t.y)
      return 1;
    else if (tp[mid].x < t.x || (tp[mid].x == t.x && tp[mid].y < t.y))
      l = mid + 1;
    else
      r = mid - 1;
  }
  return 0;
}
int main() {
  int i, j, k, re, ri;
  while (scanf("%d", &n) != EOF) {
    for (i = 0; i < n; i++) scanf("%d%d", &tp[i].x, &tp[i].y);
    sort(tp, tp + n, cmp);
    for (i = 1, j = k = m = 0; i < n; i++) {
      if (!(tp[j].x == tp[i].x && tp[j].y == tp[i].y)) {
        tp[++j] = tp[i];
        if (k >= 2) m++;
        k = 0;
      } else
        k++;
    }
    n = j + 1;
    for (i = 0; i < n; i++) {
      for (j = 0; j < n; j++) {
        if (i == j) continue;
        TPoint tmp;
        tmp.x = 2 * tp[j].x - tp[i].x;
        tmp.y = 2 * tp[j].y - tp[i].y;
        if (find(tmp)) m++;
      }
    }
    printf("%d\n", m / 2);
  }
  return 0;
}
