#include<fstream>
using namespace std;
int main()
{
	ifstream in("nrtri.in");
	ofstream out("nrtri.out");
	int n,x,j,k,l,v[801],w,i;
	in>>n;
	for(i=1;i<=n;i++)
	{
		in>>x;
		v[i]=x;
	}
	w=0;
	for(j=1;j<=n;j++)
		for(k=j+1;k<=n;k++)
			for(l=k+1;l<=n;l++)
				if ((v[j]+v[k]>=v[l])&&(v[j]+v[l]>=v[k])&&(v[l]+v[k]>=v[j])) w++;
	out<<w;
	in.close();
	out.close();
	return 0;
}