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;
template <class T>
T maxT(T a, T b) {
  return (a > b ? a : b);
}
template <class T>
T minT(T a, T b) {
  return (a < b ? a : b);
}
template <class T>
void setmin(T &a, T b) {
  a = (a > b ? a : b);
}
template <class T>
void setmax(T &a, T b) {
  a = (a < b ? a : b);
}
void fileio() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
  freopen("debug.txt", "w", stderr);
}
void ofileio() {
  freopen("input.txt", "r", stdin);
  freopen("output.txt", "w", stdout);
}
void clock_out() {
  cerr << "\nTime Elapsed : " << 1.0 * clock() / CLOCKS_PER_SEC << " s\n";
}
void debug_out() { cerr << endl; }
template <typename Head, typename... Tail>
void debug_out(Head H, Tail... T) {
  cerr << " " << H;
  debug_out(T...);
}
const long long MOD = 1000000007;
const long long SIZE = 100000;
const int INF = 0x3f3f3f3f;
const long long LL_INF = 0x3f3f3f3f3f3f3f3f;
const long double PI = acos(-1);
const long long MAXN = numeric_limits<long long>::max();
long long n;
vector<pair<long long, long long>> crd(3005);
bool bs(long long left, long long mid) {
  long long x = 2 * crd[mid].first - crd[left].first;
  long long y = 2 * crd[mid].second - crd[left].second;
  long long pos =
      lower_bound(crd.begin(), crd.end(), make_pair(x, y)) - crd.begin();
  if (pos >= n) {
    return false;
  } else {
    return (crd[pos].first == x && crd[pos].second == y);
  }
}
void solve() {
  cin >> n;
  crd.resize(n);
  for (long long i = 0; i < n; i++) {
    cin >> crd[i].first >> crd[i].second;
  }
  sort(crd.begin(), crd.end());
  long long cnt = 0;
  for (long long i = 0; i < n - 1; i++) {
    for (long long j = i + 1; j < n; j++) {
      cnt += bs(i, j);
    }
  }
  cout << cnt;
}
int main() {
  ios_base::sync_with_stdio(false), cin.tie(0), cout.tie(0);
  srand(time(NULL));
  1;
  long long t = 1;
  while (t--) {
    solve();
  }
  1;
  return 0;
}
