#include<stdio.h>
//#include<algorithm>
//using namespace std;
int v[801];
int main()
{
	freopen("nrtri.in","r",stdin);
	freopen("nrtri.out","w",stdout);
	int n,i,j,l,sol=0;
	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(l=j+1;l<=n;l++)
			{
				if(v[i]+v[j]>=v[l]&&v[i]+v[l]>=v[j]&&v[j]+v[l]>=v[j])
					sol++;
				//break;
			}
	printf("%d\n",sol);
	return 0;
}