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;
const int MAXN = 3000;
const int INF = 100000000;
class Point {
 public:
  int x, y;
};
Point p[MAXN];
int max(int a, int b) { return (a > b) ? a : b; }
int min(int a, int b) { return (a < b) ? a : b; }
int cmp(const void *t1, const void *t2) {
  Point *a, *b;
  a = (Point *)t1;
  b = (Point *)t2;
  if (a->x < b->x || (a->x == b->x && a->y < b->y))
    return -1;
  else
    return 1;
}
int bsearch(const Point &tp, int size) {
  int low, mid, high;
  low = 0;
  high = size - 1;
  while (low <= high) {
    mid = low + (high - low) / 2;
    if (p[mid].x == tp.x && p[mid].x == tp.x) {
      return mid;
    }
    if (p[mid].x < tp.x || (p[mid].x == tp.x && p[mid].y < tp.y)) {
      low = mid + 1;
    } else {
      high = mid - 1;
    }
  }
  return -1;
}
int main() {
  Point p1, p2, tp;
  int N, result;
  while (1 == scanf("%d", &N)) {
    p1.x = p1.y = INF;
    p2.x = p2.y = -INF;
    for (int i = 0; i < N; i++) {
      scanf("%d%d", &p[i].x, &p[i].y);
      p1.x = min(p1.x, p[i].x);
      p1.y = min(p1.y, p[i].y);
      p2.x = max(p2.x, p[i].x);
      p2.y = max(p2.y, p[i].y);
    }
    result = 0;
    for (int i = 0; i < N; i++) {
      for (int j = i + 1; j < N; j++) {
        tp.x = 2 * p[j].x - p[i].x;
        tp.y = 2 * p[j].y - p[i].y;
        if (tp.x < p1.x || tp.x > p2.x || tp.y < p1.y || tp.y > p2.y) continue;
        if (bsearch(tp, N) >= 0) result++;
      }
    }
    printf("%d\n", result);
  }
  return 0;
}
