#include <fstream>
using namespace std;
ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int main()
{
    int N, a[800], nrtri = 0, maxc = 0, aux = 0
    ;
    bool ok;
    fin >> N;
    for(int i = 0; i < N; i++)
        fin >> a[i];

    do
    {
        ok = true;
        for(int i = 0; i < N-1; i++)
            if(a[i] > a[i+1])
            {
                aux = a[i];
                a[i] = a[i+1];
                a[i+1] = aux;
                ok = false;
            }
    } while(!ok);

    for(int i = 0; i < N - 2; i++)
    {
        maxc = a[i] + a[i+1];
        for(int j = i+2; j < N; j++)
        {
            if(a[j] > maxc)
                break;
            nrtri++;
        }
    }
    fout << nrtri;
    return 0;
}