#include <fstream>
#include <algorithm>

using namespace std;

ifstream fin("nrtri.in");
ofstream fout("nrtri.out");

int v[800];

int cautare(int x, int st, int dr)
{

    int m;
    while (st < dr)
    {

        m = st + (dr - st) / 2;
        if (v[m] <= x)
            st = m + 1;
        else
            dr = m;
    }
    return st - 1;

}


int main()
{

    int n, i, j, poz, cnt;
    fin >> n;
    for (i = 0; i < n; i++)
        fin >> v[i];
    sort(v, v + n);
    cnt = 0;
    for (i = 0; i < n - 1; i++)
    {
        for (j = i + 1; j < n; j++)
        {

            cnt += cautare(v[i] + v[j], j + 1, n) - j;

        }
    }
    fout << cnt;

    return 0;

}