# include <fstream.h>

# define input "nrtri.in"
# define output "nrtri.out"

# define max 801

long a[max],n,i,rez,j,k,aux;

int main()
{
	ifstream fin ( input ) ;
	ofstream fout ( output ) ;

	fin >> n;

	for(i = 1;i<=n;i++)
		fin >> a[i];

	for(i = 1;i<=n-1;i++)
		for(j = i+1;j<=n;j++)
			if(a[i] > a[j])
			{
				aux = a[i];
				a[i] = a[j];
				a[j] = aux;
			}

	for(i = 1;i<=n-2;++i)
		for(j = i+1;j<=n-1;++j)
			for(k = j+1;k<=n;++k)
			{
				if(a[i] + a[j] >= a[k])
					rez++;
				else
					break;
			}

	fout << rez;

	return 0;
}