#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,j,k,v[801],rez;

int main()
{
	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-2;i++)
		for (j=i+1;j<=n-1;j++)
			for (k=j+1;k<=n;k++)
				if (v[k]<=v[i]+v[j]) rez++;
	printf("%d\n",rez);
	return 0;
}