#include<fstream>
#include<algorithm>

#define Nmax 810

using namespace std;

int n, a[Nmax], sol;

int main()
{
    ifstream f("nrtri.in");
    ofstream h("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 - 2; ++i)
        for (int j = i + 1; j <= n - 1; ++j)
            for (int k = j + 1; k <= n && a[i] + a[j] >= a[k]; ++k)
                sol++;
    h << sol << '\n';
    h.close();
    return 0;
}