#include <fstream>
#include <algorithm>
using namespace std;

ifstream f("nrtri.in");
ofstream g("nrtri.out");

short n, nr;
int LG[30001], i, j, k;

int main()
{
    f >> n;

    for (i = 1; i <= n; i++)
        f >> LG[i];

    sort (LG+1, LG+n+1);
    nr = 0;
    for (i = 1; i < n; i++)
        for (j = i+1; j <= n; j++)
            for (k = j+1; LG[k] >= LG[i]+LG[j]; k++)
                nr++;
    g << nr << "\n";
    return 0;
}