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