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