#include <fstream>
#include <algorithm>

using namespace std;

const int L = 9;

int main()
{
    ifstream in("nrtri.in");
    ofstream out("nrtri.out");

    int v[1001], n, i, j, k, pas, rez = 0;

    in >> n;
    for(i=1; i<=n; i++) {
        in >> v[i];
    }
    sort(v + 1, v + n + 1);
    for (i = 1; i < n - 1; i++) {

        k = i+2;
        for (j = i + 1; j < n; j++)
        {
            while ( k <= n && v[k] <= v[i] + v[j] )
                k++;

            if (k > j)
                rez += k - j - 1;
        }
    }
    out << rez;

    return 0;
}