#include<fstream>
#include<algorithm>

using namespace std;
ifstream fi("nrtri.in");
ofstream fo("nrtri.out");

int n,x[820],i,j,cont=0;

void citire()
{
	fi>>n;
	
	for(i=1; i<=n; i++)
		fi>>x[i];
	
	sort(x+1, x+n+1);
}

void cautare()
{
	cont=0;
	
	for(i=1; i<=n; i++)
		for(j=i+1; j<=n; j++)
		{
			for(int p=j+1; p<=n; p++)
			{
				if(x[i]+x[j]<=x[p])
				{
					cont+=n-p+1;
					break;
				}
			}
		}
		
	fo<<cont;
}

void sfarsit()
{
	fi.close();
	fo.close();
}

int main()
{
	citire();
	cautare();
	sfarsit();
	
	return 0;
}