#include<fstream>
#include<algorithm>
using namespace std;
int main()
{
	long i,n,l,j,k,aux;
	long v[3001];
	ifstream fin("nrtri.in");
	ofstream fout("nrtri.out");
	fin>>n;
	k=0;
	for(i=1;i<=n;i++)
		fin>>v[i];
	for(i=0;i<=n-1;i++)
		if(v[i]>v[i+1])
		{aux=v[i];
		v[i]=v[i+1];
		v[i+1]=aux;
		}
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
		   for(l=j+1;l<=n;l++)
			if(v[i]+v[j]>=v[l])k++;
	fout<<k;
	fin.close();
	fout.close();
	return 0;
}