#include <cstdio>
#include <algorithm>
#include <fstream>

using namespace std;

ifstream in("nrtri.in");
ofstream out("nrtri.out");

int v[805],n;

int main ()
{
	int st,dr,nr=0;
	in>>n;
	for (int i=1; i<=n; i++)
		 in>>v[i];
	sort (&v[1],&v[n+1]);
	
	for (int i=1; i<=n; i++)
	{
		dr=i+1;
		for(st=i+1; st<n; st++)
		{
			while(v[i]+v[st]>=v[dr] && dr<=n && v[st]<=v[i]+v[dr])
				dr++;
			nr+=dr-st-1;
		}
	}
	out<<nr;
	return 0;
}