#include<fstream>
#include<algorithm>
#define NN 801
using namespace std;
ofstream out("nrtri.out");
int main()
{
	ifstream in("nrtri.in");
	int v[NN],n,rez=0;
	in>>n;
	for(int i=1;i<=n;i++)
		in>>v[i];
	sort(v+1,v+n+1);
	for(int i=1;i<n-1;i++)
		for(int j=i+1;j<n;j++)
			for(int k=j+1;k<=n;k++)
				if(v[i]+v[j]>=v[k])
					++rez;
				else
					break;
				out<<rez;
}