#include<cstdio>
#include<algorithm>
using namespace std;
long i,j,n,k,nrt,x[2012];
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%ld",&n);
	for(i=1;i<=n;i++)
		scanf("%ld",&x[i]);
	sort(x+1,x+n+1);
	for(i=1;i<=n-2;i++)
		for(j=i+1;j<n;j++)
		{
			for(k=j+1;k<=n && x[i]+x[j]>=x[k];k++)
				nrt++;
		}
	printf("%ld\n",nrt);
	return 0;
}