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

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

int main()
{
    int x[1005];
    int n;
    fin >> n;

    for (int i = 1; i <= n; i++)
        fin >> x[i];

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

    long long cnt = 0;

    for (int i = 1; i <= n - 2; i++)
    {
        for (int j = i + 1; j <= n - 1; j++)
        {
            int suma = x[i] + x[j];
            int st = j + 1, dr = n;
            int poz = j; 
            while (st <= dr)
            {
                int mid = st + (dr - st) / 2;
                if (x[mid] <= suma)
                {
                    poz = mid;   
                    st = mid + 1;    
                }
                else
                    dr = mid - 1;    
                
            }
            if (poz > j)
                cnt += (poz - j);
        }
    }

    fout << cnt;


    return 0;
}