#include<stdio.h>
#include<algorithm>
using namespace std;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n,v[850];
	scanf("%d",&n);
	for(int i=1;i<=n;i++)
		scanf("%d",&v[i]);
	sort(v+1,v+n);
	int poz=0,i,j,k=3;
	for(i=1;i<=n;i++)
		for(j=i+1;j<=n;j++)
			for(;v[k]<=v[i]+v[j];k++)
				if(v[i]+v[j]>=v[k])
					poz++;
	printf("%d\n",poz);
	return 0;
}