#include <cstdio>
#include <algorithm>
using namespace std;

short b[801];

int main()
{
	int n,i,j,k,lim,nr=0;
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;++i)
		scanf("%d",&b[i]);
	sort(b,b+n+1);
	for(i=1;i<=n-2;++i)
		for(j=i+1;j<=n-1;++j)
		{
			lim=b[i]+b[j];
			for(k=j+1;b[k]<=lim&&k<=n;++k)
				++nr;
		}
	printf("%d",nr);
	return 0;
}