# include<stdio.h>
int n,v[801],i,a,b,c,j,h,contor;
int main()
{
	freopen(" nrtri.in" , "r" , stdin);
	freopen("nrtri.out" , "w" , stdout);
	contor=0;
	scanf("%d", &n);
	for(i=0;i<n;i++)
	{
		scanf("%d", &v[i]);
	}
	for(i=0;i<n-2;i++)
	for(j=i+1;j<n-1;j++)
	for(h=j+1;h<n;h++)
	if ( ( v[i]+v[j]>=v[h]  )&& (v[i]+v[h]>=v[j]  )&&( v[j]+v[h]>=v[i]   ) )
	{
		contor++;
	}
	printf("%d", contor);
	fclose(stdin);
	fclose(stdout);
	return 0;
}