#include <fstream>
#include <algorithm>

using namespace std;

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

int n, i, j, nr, dr;
int a[801];

int cmp(int x, int y)
{   return x < y;   }

int main()
{
    f >> n;
    for (i = 1; i <= n; i++)
        f >> a[i];

    sort(a+1, a+n+1, cmp);

    for (i = 1; i < n-1; i++)
        for (j = i+1; j < n; j++)
            for (dr = j+1; dr <= n; dr++)
                if (a[i] + a[j] < a[dr])
                    nr++;
    g << nr;
    return 0;
}