#include<fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");

int main ()
{
	int a[801],n,i,j,k,cont;
	f>>n;
	for (i=1; i<=n; i++)
		f>>a[i];
	cont=0;
	for (i=1; i<=n-2; i++)
		for (j=i+1; j<n; j++)
			for (k=j+1; k<=n; k++)
				if (a[i]+a[j]>=a[k] && a[j]+a[k]>=a[i] && a[i]+a[k]>=a[j]) cont++;
	g<<cont;
	return 0;
}