#include <fstream>
#include <algorithm>
using namespace std;

ifstream citit("nrtri.in");
ofstream afisi("nrtri.out");
int b[801];

int main()
{
	int n,i,j,k,lim,nr=0;
    citit>>n;
	for(i=1;i<=n;++i)
		citit>>b[i];
	sort(b,b+n+1);
	for(i=1;i<=n-2;++i)
		for(j=i+1;j<=n-1;++j)
		{
			lim=b[i]+b[j];
			for(k=j+1;b[k]<=lim&&k<=n;++k)
				++nr;
		}
    afisi<<nr;
	return 0;
}