#include<cstdio>
#include<algorithm>
using namespace std;
int n,i,v[801],j,x,rasp,q;
int caut2(int x)
{
	int p=0,pas=1<<15;
	while(pas!=0)
	{
		if(p+pas<=n && v[p+pas]<=x)
			p+=pas;
		pas/=2;
	}
	return p;
}
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-1;i++)
		for(j=i+1;j<n;j++)
			{
				q=caut2(v[i]+v[j]);
				rasp+=q-j;
			}
	printf("%d",rasp);
}