#include<fstream>
#include<algorithm>
using namespace std;
ifstream in("nrtri.in");
ofstream out("nrtri.out");

int v[2003], n, s;

int bs(int i, int j)
{
	int hi = n, lo = j, val = v[i] + v[j], mid = (hi + lo) / 2;

/*	while(hi - lo>1)
	{
		if(v[mid]<=val && (v[mid + 1]>val || mid+1==n))
			return mid;
		if(v[mid]>=val)
			hi = mid;
		else
			lo = mid;

		mid = (hi + lo)/2;
	}

	if(v[mid]<=val && v[mid + 1]>val)
			return mid;
	if(v[hi]<=val && v[hi + 1]>val)
			return hi;
	if(v[lo]<=val && v[lo + 1]>val)
			return lo;*/
	int n2, step, sol;
            for ( n2 = 1; 2*n2<=val; n2 *= 2 ){
            }
            sol = j;
            for ( step = n2; step>0; step /= 2 ) {
                if ( sol+step<n && v[sol+step]<=val )
                    sol += step;
            }
			return sol;
}
int main(){
	int player_unu=0;

	in>>n;
	for(int i = 0; i<n; i++)
		in>>v[i];

	sort(v,v+n);

	for(int i = 0; i<n; i++)
	{
		for(int j = i + 1; j<n; j++)
			s += bs(i, j) - j;
	}

	out<<s;

	return player_unu;
}