#include <fstream>
#include <algorithm>
using namespace std;
fstream fin("nrtri.in",ios::in),fout("nrtri.out",ios::out);
int main()
{
	long n,i,j,k,cate=0,ok;
	long a[30003],aux;
	fin>>n;
	for (i=1;i<=n;i++)
	{
		fin>>a[i];
	}
	sort(a+1,a+n+1);
	for (i=1;i<=n;i++)
	{
		for (j=i+1;j<=n;j++)
		{
			for (k=j+1;k<=n;k++)
			{
				if (a[i]+a[j]>=a[k])
				{
					cate++;
				}
				else
				{
					break;
				}
			}
		}
	}
	fout<<cate;
	fin.close();
	fout.close();
	return 0;
}