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;
long long gcd(long long a, long long b) {
  if (b == 0) return a;
  return gcd(b, a % b);
}
int n;
struct point {
  long long x, y;
  point(long long x = 0, long long y = 1) : x(x), y(y) {}
  void read() { scanf("%I64d %I64d", &x, &y); }
  void simp() {
    if (x < 0 || (x == 0 && y < 0)) x = -x, y = -y;
  }
};
point operator-(point a, point b) { return point(a.x - b.x, a.y - b.y); }
bool operator<(point a, point b) { return a.x == b.x ? a.y < b.y : a.x < b.x; }
bool operator==(point a, point b) { return a.x == b.x && a.y == b.y; }
point p[3005], q[3005];
int main() {
  int i, j;
  long long r = 0;
  scanf("%d", &n);
  for (i = 0; i < n; i++) p[i].read();
  for (i = 0; i < n; i++) {
    int nt = 0;
    for (j = 0; j < n; j++)
      if (i != j) q[nt++] = p[j] - p[i], q[nt - 1].simp();
    sort(q, q + nt);
    for (j = 0; j < nt - 1; j++)
      if (q[j] == q[j + 1]) ++r;
  }
  printf("%I64d\n", r);
  return 0;
}
