#include<fstream>
#include<algorithm>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int main()
{
	int n,i,j,k,l;
	f>>n;
	int v[n+1];
	for (i=1;i<=n;i++)
		f>>v[i];
	sort(v+1,v+n+1);
	k=0;
	for (i=1;i<=n-2;i++)
		for (j=i+1;j<=n-1;j++)
			for (l=j+1;l<=n;l++){
				if (v[i]+v[j]>=v[l]) k++;
				else break;
			}
	g<<k;
	return 0;
}