#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; }