#include<cstdio>
#include<algorithm>
using namespace std;
int n,v[805],s;
int main()
{
	int i,j;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		scanf("%d",&v[i]);
	sort(v+1,v+n+1);
	for(i=1;i<n;i++)
		for(j=i+1;j<n;j++)
			s+=(int)(upper_bound(v+j+1,v+n+1,v[i]+v[j])-(v+j+1));
	printf("%d",s);
	return 0;
}