#include<fstream>
#include<algorithm>
using namespace std;
int main()
{
	long i,n,l,j,k;
	long v[3001];
	ifstream fin("nrtri.in");
	ofstream fout("nrtri.out");
	fin>>n;
	k=0;
	for(i=1;i<=n;i++)
		fin>>v[i];
	sort(v+1,v+n+1);
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
		   for(l=j+1;l<=n;l++)
			if((v[i]+v[j]>=v[l])&&(v[i]+v[l]>=v[j])&&(v[l]+v[j]>=v[i]))k++;
	fout<<k;
	fin.close();
	fout.close();
	return 0;
}