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

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

int N, v [ 1 << 10 ], 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 [ J ] )
		{
			cnt += i - J;
			break;
		}
}
/*
void BS ( int I, int J )
{
	int hi = N, lo = J + 1, mid;
	
	while ( hi >= lo )
	{
		mid = lo + ( ( hi - lo ) / 2 );
		if ( v [ mid ] > v [ I ] + v [ J ] )
			hi = mid - 1;
		else 
			break;
	}
	
	if ( v [ mid ] <= v [ I ] + v [ J ] )
		cnt += mid - J;
}
*/
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; ++i )
		for ( int j = i + 1; j <= N; ++j )
			BS ( i, j );
	
	out << cnt;
	
	return 0;
}