#include<iostream>
#include<cstdio>
using namespace std;
int a[1000],n,i,j,k,nr;
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=1;i<=n;i++)
		scanf("%d",&a[i]);
	sort(a+1,a+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(a[i]+a[j]>=a[k])
					nr++;
				else break;
	printf("%d\n",nr);
	return 0;
}