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 N = 3005;
struct coord {
  int x, y;
};
bool operator<(coord left, coord right) {
  if (left.x < right.x) {
    return true;
  } else if (left.x == right.x) {
    if (left.y < right.y) {
      return true;
    } else
      return false;
  } else
    return false;
}
coord a[N], d[N];
int n, i, s, f, j, q;
int binarysearch(int x, int y);
int main() {
  cin >> n;
  for (i = 1; i <= n; ++i) {
    cin >> s >> f;
    a[i].x = s;
    a[i].y = f;
  }
  sort(a + 1, a + 1 + n);
  for (i = 1; i <= n; ++i) {
    d[i].x = a[i].x * 2;
    d[i].y = a[i].y * 2;
  }
  q = 0;
  for (i = 1; i < n; ++i) {
    for (j = i + 1; j <= n; ++j) {
      if (i != j) {
        q += binarysearch(a[i].x + a[j].x, a[i].y + a[j].y);
      }
    }
  }
  cout << q << endl;
  return 0;
}
int binarysearch(int x, int y) {
  int sx, fx, m = 0;
  coord e;
  e.x = x;
  e.y = y;
  if (d[1].x == e.x && d[1].y == e.y && i != 1 && j != 1) {
    return 1;
    goto x;
  }
  if (d[n].x == e.x && d[n].y == e.y && i != n && j != n) {
    return 1;
    goto x;
  }
  sx = 1;
  fx = n;
  while (m == 0) {
    if (d[(sx + fx) / 2] < e && e < d[fx]) {
      sx = (sx + fx) / 2;
      if (d[sx].x == e.x && d[sx].y == e.y && sx != i && sx != j) {
        return 1;
        m = 1;
        goto x;
      }
      if (d[fx].x == e.x && d[fx].y == e.y && fx != i && fx != j) {
        return 1;
        m = 1;
        goto x;
      }
      if (abs(fx - sx) <= 1) {
        if (d[sx].x == e.x && d[sx].y == e.y && sx != i && sx != j) {
          return 1;
          m = 1;
          goto x;
        }
        if (d[fx].x == e.x && d[fx].y == e.y && fx != i && fx != j) {
          return 1;
          m = 1;
          goto x;
        }
        return 0;
      }
    } else if (d[sx] < e && e < d[(sx + fx) / 2]) {
      fx = (sx + fx) / 2;
      if (d[sx].x == e.x && d[sx].y == e.y && sx != i && sx != j) {
        return 1;
        m = 1;
        goto x;
      }
      if (d[fx].x == e.x && d[fx].y == e.y && fx != i && fx != j) {
        return 1;
        m = 1;
        goto x;
      }
      if (abs(sx - fx) <= 1) {
        if (d[sx].x == e.x && d[sx].y == e.y && sx != i && sx != j) {
          return 1;
          m = 1;
          goto x;
        }
        if (d[fx].x == e.x && d[fx].y == e.y && fx != i && fx != j) {
          return 1;
          m = 1;
          goto x;
        }
        return 0;
      }
    }
    if (d[sx].x == e.x && d[sx].y == e.y && sx != i && sx != j) {
      return 1;
      goto x;
      m = 1;
    }
    if (d[fx].x == e.x && d[fx].y == e.y && fx != i && fx != j) {
      return 1;
      goto x;
      m = 1;
    }
    if (d[(sx + fx) / 2].x == e.x && d[(sx + fx) / 2].y == e.y &&
        (sx + fx) / 2 != i && (sx + fx) / 2 != j) {
      return 1;
      goto x;
      m = 1;
    }
    m = 1;
    goto x;
  }
  return 0;
x:
  int prosto;
}
