#include <algorithm>
#include <fstream>

using namespace std;

int main()
{
    int n,a[801],i,u,j,y,nr=0;
    ifstream fin("nrtri.in");
    ofstream fout("nrtri.out");
    fin>>n;
    for (y=1;y<=n;y++)
    {
        fin>>a[y];
    }
    sort(a+1,a+n+1);
    for (i=1;i<=n-2;i++)
    {
        for (j=i+1;j<=n-1;j++)
        {
            for (u=j+1;u<=n;u++)
            {
                if (a[i]+a[j]>=a[u] && a[i]+a[u]>=a[j] && a[j]+a[u]>=a[i])
                    nr=nr+1;
                if (a[u]>a[i]+a[j])
                    break;
            }
        }
    }
    fout<<nr;
    fin.close();
    fout.close();
    return 0;
}