#include <fstream>
#include <algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int v[801],i,n,k=0,j,r;
int main()
{
    f>>n;
    for (i=1;i<=n;i++)
    {
        f>>v[i];
    }
    sort (v+1,v+n+1);
    for (i=1;i<=n-2;i++)
    {
        for (j=i+1;j<=n-1;j++)
        {
            for (r=j+1;r<=n;r++)
            {
                if (v[i]+v[j]>=v[r])
                {
                    k++;
                }
            }
        }
    }
    g<<k;
    return 0;
}