#include <algorithm>
#include <fstream>

using namespace std;

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

int v[801];

bool triunghi(int i, int j, int k)
{
    return (v[i] + v[j] >= v[k]);
}

int main()
{
    int n, i, j, k, pas, nr;

    in>>n;
    for(i = 1; i <= n; i++)
        in>>v[i];

    sort(v + 1, v + n + 1);

    nr = 0;
    for(i = 1; i <= n - 2; i++)
        for(j = i + 1; j <= n - 1; j++)
        {
            k = j + 1;
            pas = 1 << 9;
            while(pas)
            {
                if(k + pas <= n && triunghi(i, j, k + pas))
                    k += pas;
                pas /= 2;
            }
            if(triunghi(i, j, k))
                nr += k - j;
        }

    out<<nr<<'\n';
    return 0;
}