#include <fstream>
using namespace std;
#include<algorithm>
int main ()
{
	int N,i,v[800],j,k,nr=0;
	ifstream fcin ("nrtri.in");
	ofstream fcout ("nrtri.out");
	fcin>>N;
	for (i=0;i<N;i++)
		fcin>>v[i];
	sort(v,v+N);
	for (i=0;i<=N-3;i++)
		for (j=i+1;j<=N-2;j++)
			for (k=j+1;k<=N-1;k++)
				if (v[i]+v[j]>=v[k])
					nr++;
				else
					break;
	fcout<<nr;
	fcin.close ();
	fcout.close ();
	return 0;
}