#include<stdio.h>
#include<algorithm>
using namespace std;
int v[801];
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n;
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
		scanf("%d",&v[i]);
	sort(v+1,v+n+1);
	int k=3,posib=0;
	for(int i=1;i<=n;i++)
	{
		for(int j=i+1;j<=n;i++){
		while(k<=n&&v[k]<=v[i]+v[j])
			k++;
		posib+=k-j;}
	}
	printf("%d\n",posib);
	return 0;
}