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 <typename T>
using min_heap = priority_queue<T, vector<T>, greater<T>>;
template <typename T>
using max_heap = priority_queue<T>;
struct custom_hash {
  static uint64_t splitmix64(uint64_t x) {
    x += 0x9e3779b97f4a7c15;
    x = (x ^ (x >> 30)) * 0xbf58476d1ce4e5b9;
    x = (x ^ (x >> 27)) * 0x94d049bb133111eb;
    return x ^ (x >> 31);
  }
  size_t operator()(uint64_t x) const {
    static const uint64_t FIXED_RANDOM =
        chrono::steady_clock::now().time_since_epoch().count();
    return splitmix64(x + FIXED_RANDOM);
  }
};
long long binpow(long long base, long long exp) {
  long long mod = 1000000007LL;
  long long res = 1;
  while (exp > 0) {
    if (exp % 2 == 1) res = (res * base) % mod;
    exp = exp >> 1;
    base = (base * base) % mod;
  }
  return res;
}
long long mod(long long x) {
  return ((x % 1000000007LL + 1000000007LL) % 1000000007LL);
}
long long add(long long a, long long b) { return mod(mod(a) + mod(b)); }
long long mul(long long a, long long b) { return mod(mod(a) * mod(b)); }
bool isPrime(long long n) {
  if (n <= 1) return false;
  for (long long i = 2; i * i <= n; i++)
    if (n % i == 0) return false;
  return true;
}
const long long N = (long long)1e6;
void sieve(long long N) {
  bool prime[N + 1];
  memset(prime, true, sizeof(prime));
  for (long long p = 2; p * p <= N; p++) {
    if (prime[p] == true) {
      for (long long i = p * p; i <= N; i += p) prime[i] = false;
    }
  }
}
long long fact(long long n) {
  long long res = 1;
  for (long long i = 1; i <= n; i++) {
    res = res * 1ll * i % 1000000007LL;
  }
  return res;
}
long long C(long long n, long long k) {
  return fact(n) * 1ll * binpow(fact(k), 1000000007LL - 2) % 1000000007LL *
         1ll * binpow(fact(n - k), 1000000007LL - 2) % 1000000007LL;
}
int32_t main() {
  ios_base::sync_with_stdio(false);
  cin.tie(NULL);
  cout.tie(NULL);
  long long n;
  cin >> n;
  set<pair<long long, long long>> st;
  vector<pair<long long, long long>> v;
  for (long long i = 0; i < n; i++) {
    long long a, b;
    cin >> a >> b;
    v.push_back(make_pair(a, b));
    st.insert(make_pair(a, b));
  }
  long long ans = 0;
  for (long long i = 0; i < n; i++) {
    for (long long j = i + 1; j < n; j++) {
      long long x = v[i].first + v[j].first;
      long long y = v[i].second + v[j].second;
      if (x % 2 == 0 && y % 2 == 0) {
        x = x / 2;
        y = y / 2;
        if (st.find({x, y}) != st.end()) {
          ans++;
        }
      }
    }
  }
  cout << ans << "\n";
  return 0;
}
