#include <fstream>
#include <algorithm>
using namespace std;
int v[3001];
int main()
{
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");
	int i,n,j,r,k,x;
	f>>n; k=0;
	for (i=1;i<=n;i++)
	{
		f>>x;
		v[i]=x;
	}
	sort(v+1,v+n+1);
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			for(r=j+1;r<=n;r++)
				if(v[r]<=v[i]+v[j])k++;
	g<<k;
	f.close();
	g.close();
	return 0;
}