#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;
}