#include<iostream>
#include<fstream>
#define NMax 80100

using namespace std;

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

int V[NMax],i,n,rez,j,k;

bool cmp(int i, int j)
{
	return j>i;
}

int main()

{ 
	fin>>n;
	for(i=0;i<n;i++)
		fin>>V[i];
	sort(V,V+n,cmp);
	for(i=0;i<n-1;i++)
		for(j=i+1;j<n;j++)
		{
			for(k=j+1;V[i]+V[j]<=V[k] && k<n;k++);
			rez+=k-j;
		}
	fout<<rez;
	return 0;
}