#include<fstream>  
#include<algorithm>
#include<math.h>
using namespace std;

ifstream in("nrtri.in");  
ofstream out("nrtri.out");  

int v[1000],i,j,e,n,s,a,b;  
int main()  
{  
in>>n;  
for(i=1; i<=n; i++)  
    in>>v[i];  
  
  
for(i=1; i<n-1; i++)  
    for(j=i+1; j<n; j++)  
		{
		a=upper_bound(v+j+1,v+n+1,v[j]+v[i]);
		b=lower_bound(v+j+1,v+n+1,abs(v[j]-v[i]));
		s+=a-b+1;
        /*for(e=j+1; e<=n; e++)  
            if(v[i]+v[j]>=v[e] && v[j]+v[e]>=v[i] && v[i]+v[e]>=v[j])  
                s++;  */
        }
out<<s;  
out<<'\n';  
return 0;  
}