#include<fstream>
#include<algorithm>

using namespace std;

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

const short MAX = 800;

int N, v[MAX], rasp;

int i,j,k;

inline void citeste()
{
	in>>N;
	for(i=0; i<N; i++)
		in>>v[i];
}

inline void rezolva()
{
	sort(v,v+N);
	for(i=0; i<N-2; i++)
		for(j=i+1; j<N-1; j++)
			for(k=j+1; k<N; k++)
				if(v[i]+v[j]>=v[k])
					rasp++;
				else break;
}

inline void scrie()
{
	out<<rasp<<'\n';
}

int main()
{
	citeste();
	rezolva();
	scrie();
	return 0;
}