#include <cstdio>
#include <algorithm>
#include <fstream>
using namespace std;

int x[1000];

bool cmp(int a,int b)
{
	return a<b;
}

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

int main()
{
	
	int n,i,st,dr,nr=0;
	in>>n;
	for(i=1;i<=n;i++)
	{
		in>>x[i];
	}
	
	sort(&x[1],&x[n+1],cmp);
	
	for(i=1;i<=n;i++)
	{
		dr=i+1;
		for(st=i+1;st<=n;st++)
		{
			while(dr<=n && x[i]+x[st]>=x[dr] && x[st]<=x[i]+x[dr])
			{
				dr++;
			}
			nr+=dr-st-1;
		}
	}
	

	out<<nr<<"\n";
	
	return 0;
}