#include <fstream>
using namespace std;
fstream fin("nrtri.in",ios::in),fout("nrtri.out",ios::out);
int main()
{
	int n,i,j,k,cate=0,ok;
	long long a[30001],aux;
	fin>>n;
	for (i=1;i<=n;i++)
	{
		fin>>a[i];
	}
	do
	{
		ok=1;
		for (i=1;i<n;i++)
		{
			if (a[i]>a[i+1])
			{
				aux=a[i];
				a[i]=a[i+1];
				a[i+1]=aux;
				ok=0;
			}
		}
	}while (ok==0);
	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++;
				}
			}
		}
	}
	fout<<cate;
	fin.close();
	fout.close();
	return 0;
}