#include<iostream>
#include<fstream>
using namespace std;
int k,n,v[8001];
int main()
{
	ifstream fin("nrtri.in");
	ofstream fout("nrtri.out");
	int aux,i,j,l;
	fin>>n;
	for(i=1;i<=n;i++)
	   fin>>v[i];
	for(i=1;i<=n-1;i++)
		for(j=i+1;j<=n;j++)
			if(v[i]>v[j])
			{
				aux=v[i];
				v[i]=v[j];
				v[j]=aux;
			}
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			for(l=j+1;l<=n;l++)
				if(v[i]+v[j]>=v[l])k++;
	fout<<k;
	return 0;
}