#include<stdio.h>

int a[1000],n;
void sortare()
{
	int i,sort,aux;
	sort = 0;
	while(sort==0)
	{
		sort = 1;
		for(i=1;i<=n-1;i++)
		
			if(a[i] > a[i+1])
			{
				aux = a[i];
				a[i] = a[i+1];
				a[i+1] = aux;
				sort = 0;
			}
	}
	
}

int main()
{
	int i,s,j,k;
	
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	
	scanf("%d",&n);
	
	for(i=1;i<=n;i++)
		scanf("%d",&a[i]);
		
	sortare();
	s = 0;
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			
			if(a[i] + a[j] >= a[n])
			{
					s += n - j   ;
					
			}
			
	
	printf("%d",s);
	return 0;
}