// By Stefan Radu
#include <fstream>
#include <algorithm>
using namespace std;
ifstream cin("nrtri.in");
ofstream cout("nrtri.out");
#define sz(x) (int)(x).size()
typedef pair < int, int > pii;
typedef long long ll;
typedef long double ld;
typedef unsigned int ui;
typedef unsigned long long ull;
const int MAX_CNT = 30001, MAX_N = 800;
int mars[MAX_CNT], lengths[MAX_N];
int main() {
#ifdef STEF
  freopen("input", "r", stdin);
  freopen("output", "w", stdout);
#endif
  ios::sync_with_stdio(false);
  cin.tie(0);cout.tie(0);
  int n; cin >> n;
  for (int i = 0; i < n; ++ i) {
    cin >> lengths[i];
    mars[lengths[i]] += 1;
  }
  sort(lengths, lengths + n);
  for (int i = 1; i < MAX_CNT; ++ i) mars[i] += mars[i - 1];
  int cnt = 0;
  for (int i = 0; i < n; ++ i) {
    for (int j = i + 1; j < n; ++ j) {
      int a = max(0, lengths[j] - lengths[i] - 1);
      int b = min(lengths[i] + lengths[j], 30000);
      cnt += mars[b] - mars[a];
      cnt -= a < lengths[i] ? 2 : 1;
    }
  }
  cout << cnt / 3 << '\n';
}