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

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

const int NMax = 1 << 10;
int N, v [ NMax ], cnt;

bool comp ( int a, int b )
{
	return a < b;
}

void BS ( int I, int J )
{
	for ( int i = N; i > J; --i )
		if ( v [ i ] >= v [ I ] && v [ i ] >= v [ J ] && v [ i ] <= v [ I ] + v [ J ] )
		{
			cnt += i - J;
			break;
		}
}

int main ()
{
	in >> N;
	for ( int i = 1; i <= N; ++i )
		in >> v [ i ];
	
	sort ( v + 1, v + N + 1, comp );
	
	for ( int i = 1; i <= N / 2; ++i )
		for ( int j = i + 1; j <= N; ++j )
			BS ( i, j );
	
	out << cnt;
	
	return 0;
}