#include<fstream>
#include<algorithm>
using namespace std;

int n, b[801];

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

    fin >> n;
    for (int i = 1; i <= n; ++i)
        fin >> b[i];
    sort(b + 1, b + n + 1);

    long long count = 0;
    for (int i = 1; i < n; ++i)
        for (int j = i + 1; j <= n; ++j)
        {
            int t2 = upper_bound(b + 1, b + n + 1, b[i] + b[j]) - (b + 1) - 1;
            count += t2 - j + 1;
        }
    fout << count;

    return 0;
}