#include <fstream>
using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,a,b,c,sa,i,v[801],sb,sc,k;
int main()
{
    fin>>n;
    for (i=1; i<=n; i++)
        fin>>v[i];
    for (a=1; a<=n; a++)
    {
        for (b=a+1; b<=n; b++)
        {
            for (c=b+1; c<=n; c++)
            {
                sa=v[b]+v[c];
                sb=v[a]+v[c];
                sc=v[a]+v[b];
                if (sa>=v[a]&&sb>=v[b]&&sc>=v[c])
                    k++;
            }
        }
    }
    fout<<k;
    return 0;
}