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