#include <stdio.h>
#include <algorithm>
using namespace std;
int main()
{int nr=0,n,v[800],i,j,k;
 
freopen("nrtri.in","r",stdin);
freopen("nrtri.out","w",stdout);
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++)
	 {int* p=upper_bound(v+j+1, v + n+1, v[i]+v[j]);
	  nr+=(p-v)-j-1;
	  
	 }
printf("%d",nr);
return 0;}