#include<fstream.h>
int main()
{
	ifstream f("nrtri.in");
	ofstream g("nrtri.out");

	int n,a[800],i,j,k,nr=0;

	f>>n;

	for(i=1;i<=n;i++)
		f>>a[i];

	for(i=1;i<=n-2;i++)
		for(j=i+1;j<=n-1;j++)
			for(k=j+1;k<=n;k++)
				{
				   if((a[i]+a[j]>=a[k])&&(a[i]+a[k]>=a[j])&&(a[j]+a[k]>=a[i]))
					nr++;
				   else
				       if(a[i]+a[j]<=a[k])
					  break;
				}		
	g<<nr;
	return 0;
}