#include <fstream>

#include <fstream>
 using namespace std;
 ifstream in ("nrtri.in");
  ofstream out ("nrtri.out");
   int n, V[1000], bull, moduri, i, j, k, aux;
    void sortare()
    { int bull = 0;
     while (bull == 0)
        { bull = 1;
     for (i = 1; i < n; i++)
        { if (V[i] > V[i + 1])
        { aux = V[i];
     V[i] = V[i+1];
      V[i+1] = aux; bull = 0;
       } } } }
       void rezolvare()
       { moduri = 0;
        for (i = 1; i <= n - 2; i++)
            for (j = i + 1; j <= n - 1;j++)
                for (k = j + 1; k <= n; k++)
                { if (V[i] + V[j] >= V[k])
                { moduri++; }
            else { k = n + 1; } } }
             int main() { in >> n;
              for (i = 1; i <= n; i++
               in >> V[i]; sortare();
                rezolvare();
                out << moduri << '\n';
                 return 0; }