#include <fstream>
#include <algorithm>

using namespace std;
ofstream fout ("nrtri.out");

int a[805], n;

void Citire()
{
    ifstream fin ("nrtri.in");
    int i;
    fin >> n;
    for (i=1; i<=n; i++)
        fin >> a[i];
    sort (a+1, a+n+1);
}
void Rezolvare()
{
    int i, j, k, solutie=0;
    for (i=1; i<=n; i++)
        for (j=i+1; j<=n; j++)
        {
            k=j+1;
            while (a[i]+a[j]>=a[k] && k<=n)
                k++;
            solutie+=k-(j+1);
        }
    fout << solutie << "\n";
}

int main()
{
    Citire();
    Rezolvare();
    return 0;
}