#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)
			return mid+1;
		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 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;
}