#include<fstream>
#include<algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");
int v[801];
int main()
{
	int n,i,j,st,dr,nr=0;
	in>>n;
	for(i=1;i<=n;i++)
		in>>v[i];
	sort(v+1,v+n+1);
	for(i=1;i<=n;i++)
	{
		dr=i+1;
		for(st=1+i;st<=n;st++)
		{
			while(dr<=n && v[i]+v[st]>=v[dr] && v[st]<=v[i]+v[dr])++dr;
			nr+=dr-st-1;
		}
	}
	out<<nr<<"\n";
	return 0;
}