#include <fstream>
using namespace std;
int v[3001];
int main()
{
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");
	int i,n,j,q,K,x,aux;
	f>>n; K=0;
	for (i=1;i<=n;i++)
	{
		f>>x;
		v[i]=x;
	}
	for (i=1;i<=n-1;i++)
		for (j=i+1;j<=n;j++)
			if (v[i]>v[j])
			{
				aux=v[i];
				v[i]=v[j];
				v[j]=aux;
			}
	for (i=1;i<=n;i++)
		for (j=i+1;j<=n;j++)
			for (q=j+1;q<=n;q++)
				if (v[q]<=v[i]+v[j])
					K++;
	g<<K;
	f.close();g.close();return 0;
}