#include<fstream>
using namespace std;
int a[800],n,i,j,k,nr,aux;
int main()
{
	ifstream f("ntri.in");
	ofstream g("ntri.out");
	f>>n;
	for(i=1;i<=n;i++)
		f>>a[i];
	for(i=1;i<=n-1;i++)
		for(j=i+1;j<=n;j++)
			if(a[i]>a[j])
			{
				aux=a[i];
				a[i]=a[j];
				a[j]=aux;
			}
	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])
					nr++;
				g<<nr;
				return 0;
}