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