#include <vector>
#include <algorithm>
#include <fstream>

using namespace std;

vector <int> a;
int x=0;

void read()
{
    int n;
    ifstream f("nrtri.in");
    f >> n;
    a.resize(n);
    for (int i=0; i<a.size(); i++)
        f >> a[i];
    f.close();
}

void write()
{
    ofstream f("nrtri.out");
    f << x;
    f.close();
}

void solve()
{
    for (int i=0; i<a.size(); i++)
    {
        for (int j=i+1; j<a.size(); j++)
        {
            for (int z=j+1; z<a.size() && a[z]<=a[i]+a[j]; z++)
            {
                x++;
            }
        }
    }
}

main()
{
    read();
    sort(a.begin(),a.end());
    solve();
    write();
}