#include <algorithm>
#include <stdio.h>
using namespace std;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int i,n,a[801],sch,j,t,s=0;
	scanf("%d",&n);
	for (i=1; i<=n; i++)   
        scanf("%d",&a[i]);   
	sort (a+1, a+n+1);
	for (i=1; i<=n-2; i++)
		for (j=i+1; j<=n-1; j++)
			for (t=n; t>=j+1; t--)
				if (a[i]+a[j]>=a[t])
				{
					s+=t-j;
                    break;
				}					
    printf("%d",s);	
	return 0;
}