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>
int popcount(T n);
template <>
int popcount(unsigned int n) {
  return n ? __builtin_popcount(n) : 0;
}
template <>
int popcount(int n) {
  return n ? __builtin_popcount(n) : 0;
}
template <>
int popcount(unsigned long long n) {
  return n ? __builtin_popcountll(n) : 0;
}
template <>
int popcount(long long n) {
  return n ? __builtin_popcountll(n) : 0;
}
template <class T>
void max_swap(T& a, const T& b) {
  a = max(a, b);
}
template <class T>
void min_swap(T& a, const T& b) {
  a = min(a, b);
}
const double EPS = 1e-8;
const double PI = acos(-1.0);
const int dx[] = {0, 1, 0, -1};
const int dy[] = {1, 0, -1, 0};
bool valid_pos(int x, int y, int w, int h) {
  return 0 <= x && x < w && 0 <= y && y < h;
}
template <class T>
void print(T a, int n, int br = 1, const string& deli = ", ") {
  cout << "{ ";
  for (int i = 0; i < n; ++i) {
    cout << a[i];
    if (i + 1 != n) cout << deli;
  }
  cout << " }";
  while (br--) cout << endl;
}
template <class T>
void print(const vector<T>& v, int br = 1, const string& deli = ", ") {
  print(v, v.size(), br, deli);
}
bool p[3333][3333];
bool& get(int x, int y) { return p[y + 1000][x + 1000]; }
int main() {
  int n, x[3333], y[3333];
  cin >> n;
  for (int i = 0; i < n; ++i) {
    cin >> x[i] >> y[i];
    get(x[i], y[i]) = true;
  }
  int res = 0;
  for (int i = 0; i < n; ++i) {
    for (int j = i + 1; j < n; ++j) {
      int tx = x[j] - x[i], ty = y[j] - y[i];
      if (!(tx & 1) && !(ty & 1) && get(tx / 2, ty / 2)) ++res;
    }
  }
  cout << res << endl;
}
