#include <fstream>
#include <algorithm>

using namespace std;

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

int n,v[805],i,j,k,numarTriunghiuri;

int main()
{
    in>>n;
    for(i=1;i<=n;i++)
		in>>v[i];
	sort(v+1,v+n+1);
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<n;j++)
			for(k=j+1;k<=n;k++)
			{
				if(v[i]+v[j]>=v[k])//&&v[j]+v[k]>=v[i]&&v[k]+v[i]>=v[j])
					numarTriunghiuri++;
				else if(v[k]>v[i]+v[j])
					break;
			}
	out<<numarTriunghiuri<<'\n';
    return 0;
}