#include<stdio.h>
#include<algorithm>
using namespace std;
int x[800],a,i,j,n,st,dr,gasit,mij,g,k;
bool cmp(int a,int b)
{
	return a>=b;
}
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	scanf("%d",&n);
	for(i=0;i<n;i++)
	{
		scanf("%d",&x[i]);
	}
	sort(x,x+n,cmp);
	for(i=0;i<n-2;i++)
	{
		for(j=i+1;j<n-1;j++)
		{
			k=j+1;
			while(k<n && x[i]<=x[j]+x[k])
			{
				k++;
			}
			g=g+k-j-1;
		}
	}
				
				printf("%d",g);
				return 0;
}