#include<cstdio>
#include<algorithm>
using namespace std;
int v[3002];
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n,k,nr=0,i,j;
	scanf("%d",&n);
	for(i=1;i<=n;i++)scanf("%d",&v[i]);
	sort(v+1,v+n+1);
	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])nr++;
	printf("%d",nr);
	return 0;
}