#include <fstream>
using namespace std;

int v[1<<10],n;

ifstream in("nrtri.in");
ofstream out("nrtri.out");

int main()
{
	int a,b,i,nr=0;
	in>>n;
	for (i=1;i<=n;i++)
		in>>v[i];
	sort(v+1,v+n+1);
	v[n+1]=1<<30;
	for (a=1;a<n-1;a++)
	{
		i=1;
		for (b=a+1;b<n;b++)
		{
			for (;v[a]+v[b]>=v[i] && i<=n;i++);
			nr+=i-b-(v[a]+v[b]<v[i]);
		}
	}
	out<<nr<<"\n";
	return 0;
}