#include<fstream>
using namespace std;
ifstream f("nrtri.in");
ofstream g("nrtri.out");
int n, x[801], nr;
int main()
{
	f>>n;
	for (int i=1;i<=n;i++) f>>x[i];
	for (int i=1;i<=n-2;i++)
		for (int j=i+1;j<=n-1;j++)
			for (int k=j+1;k<=n;k++)
				if (x[i]<=x[j]+x[k] && x[j]<=x[k]+x[i] && x[k]<=x[i]+x[k])
					nr++;
g<<nr<<"\n";
g.close();
return 0;
}