#include <fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
long n,v[801],k,nr,i,j,mij;
int main()
{
	f>>n;
	for (i=1;i<=n;i++)
		f>>v[i];
	for (i=1;i<n;i++)
		for (j=i+1;j<=n;j++)
			if (v[i]>v[j])
			{
				mij=v[i];
				v[i]=v[j];
				v[j]=mij;
			}
	for (i=1;i<n;i++)
		for (j=i+1;j<n;j++)
			for (k=j+1;k<=n;k++)
				if (v[i]+v[j]>=v[k])
					nr++;
				else
					break;
	g<<nr;
	f.close();
	g.close();
	return 0;
}