#include <fstream>

using namespace std;
ifstream cin ("nrtri.in");
ofstream cout ("nrtri.out");
int n,i,j,l,x,y,z,v[100005],ok,nr;
int main()
{
    cin >>n;
    for (i=1; i<=n; i++)
    {
        cin >>v[i];
    }
    for (i=1; i<=n; i++)
    {
        x=v[i];
        for (j=i+1; j<=n; j++)
        {
            y=v[j];
            ok=0;
            for (l=j+1; l<=n; l++)
            {
                z=v[l];
                if (x+y<=z||y+z<=x)
                {
                    ok=1; break;
                }
                else
                {
                    nr++;

                }
                //cout <<nr<<" ";
            }
            if (ok==1) {break;}
        }
    }
    cout <<nr;
    return 0;
}