// By Stefan Radu
#include <algorithm>
#include <fstream>
#include <iomanip>
#include <cassert>
#include <vector>
#include <string>
#include <cctype>
#include <queue>
#include <deque>
#include <cmath>
#include <stack>
#include <map>
#include <set>
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;
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;
  vector < int > lengths(n);
  vector < int > mars(60007);
  for (int i = 0; i < n; ++ i) {
    cin >> lengths[i];
    mars[lengths[i]] += 1;
  }
  for (int i = 1; i < sz(mars); ++ 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 = abs(lengths[i] - lengths[j]) - 1;
      int b = lengths[i] + lengths[j];
      cnt += mars[b] - mars[a];
      if (a < min(lengths[i], lengths[j])) {
        cnt -= 2;
      }
      else {
        cnt -= 1;
      }
    }
  }
  cout << cnt / 3 << '\n';
}