#include<fstream>
using namespace std;
int v[801],n,i,nr,k,j;
void quicksort(int *lp, int *rp)
{
	int max=(rp-lp)+1;
	if(max>1)
	{
		int *p=(lp+(max/2));
		int aux=0;
		while (lp!=rp)
		{
			while (*lp<*p)
				lp++;
			while (*rp>*p)
				rp--;
			if (lp==p)
				p=rp;
			else if (rp==p)
				p=lp;
			aux=*lp;
			*lp=*rp;
			*rp=aux;
			if((*lp==*p)||(*rp==*p))
				break;
		}
	}
}
int main()
{
	ifstream f("nrtri.in");
	f>>n;
	for(i=1;i<=n;i++)
		f>>v[i];
	f.close();
	quicksort(v+1,v+n+1);
	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;
	ofstream g("nrtri.out");
	g<<nr;
	g.close();
	return 0;
}