#include <fstream>
#include <algorithm>
using namespace std;
ifstream fin ("nrtri.in");
ofstream fout ("nrtri.out");
int n,i,j,k,v[802],a,b,c,tri;
int main()
{
    fin >>n;
    for (i=1;i<=n;i++)
    {
        fin >> v[i];
    }
    sort (v+1,v+n+1);
    for (i=1;i<=n-2;i++)
    {
        a=v[i];
        for (j=i+1;j<=n-1;j++)
        {
            b=v[j];
            for (k=j+1;k<=n;k++)
            {
                if (a+b>=v[k])
                {
                    tri++;
                }
            }
        }
    }
    fout << tri;
    return 0;
}