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