#include<iostream>
#include<fstream>
#include<algorithm>
using namespace std;
int n,x[152],s,q,w,nr;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	int i,j;
	for(i=1;i<=n;i++)
		scanf("%d",&x[i]);
	sort(x+1,x+n+1);
	
	for(i=1;i<n;i++)
		for(j=i+1;j<=n;j++)
		{
			q=j+1;
			w=n;
			s=x[i]+x[j];
			while(q<w)
			{
				if(x[(q+w+1)/2]>s)
					w=(q+w+1)/2-1;
				else
					q=(1+q+w)/2;
			}
			if (w==q&&s>=x[q])
				s=w;
			else s=-1;
			if (s!=-1)
				nr+=(s-j);
		}
	printf("%d",nr-1);
	
	return 0;
}