#include <cstdio>
#include <algorithm>

using namespace std;

int v[1024];

int main ()
{
    freopen ("nrtri.in", "r", stdin);
    freopen ("nrtri.out", "w", stdout);

    int n;
    scanf ("%d", &n);

    for (int i = 1; i <= n; ++i)
        scanf ("%d", &v[i]);

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

    int nr = 0;
    for (int i = 1; i <= n; ++i)
        for (int j = i + 1; j <= n; ++j)
            for (int h = j + 1; h <= n; ++h)
                if (v[i] + v[j] >= v[h]) ++nr;
                else break;

    printf ("%d\n", nr);


    return 0;
}