#include<fstream>
using namespace std;
int v[800],n;
int main()
{
	ifstream in("nrtri.in");
	ofstream out("nrtri.out");
	int i,j,k,x,ct=0;
	in>>n;
	for(i=1;i<=n;i++)
		in>>v[i];
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			if(v[i]>v[j])
				{
					x=v[i];
					v[i]=v[j];
					v[j]=x;
				}
	for(i=1;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])
					ct++;
				else
					k=n;
	out<<ct;
}