#include<fstream>
#include<algorithm>



using namespace std;

int n, a[810], sol;

int main()
{
    ifstream f("nrtri.in");
    ofstream g("nrtri.out");
    f >> n;
    for (int i = 1; i <= n; i++)
        f >> a[i];
    sort (a + 1, a + n + 1);
    f.close();

    for (int i = 1; i < n ; i++)
        for (int j = i + 1; j <= n ; j++)
            for (int k = j + 1; k <= n && a[i] + a[j] >= a[k]; k++)
                sol++;
    g << sol << "\n";
    g.close();
    return 0;
}