#include <fstream>

using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int v[10001];
int main()
{
    int n,i,j,k,nr=0;
    fin>>n;
    for (i=1; i<=n; i++)
    {
        fin>>v[i];
    }
    for (i=1; i<=n-2; i++)
    {
        for (j=i+1; j<=n-1; j++)
        {
            for (k=j+1; k<=n; k++)
            {
                if (v[j]+v[i]>=v[k]&&v[i]+v[k]>=v[j]&&v[j]+v[k]>=v[i]) nr++;

            }}}
            fout<<nr;
            return 0;
        }