#include <stdio.h>

int v[801];
int n,i,j,h,a,b,c,count;

int main ()
{
    freopen ("nrtri.in","r",stdin);
    freopen ("nrtri.out","w",stdout);
    
    scanf ("%d",&n);
    
    for (i=1;i<=n;i++) scanf ("%d",&v[i]);
    
    for (h=1;h<=n;h++){
        for (i=h+1;i<=n;i++){
            for (j=i+1;j<=n;j++){
                if ((v[h]+v[i]>=v[j])&&(v[j]+v[i]>=v[h])&&(v[h]+v[j]>=v[i])) count++;
                }
                }
                }
                
    printf ("%d",count);
    
    return 0;
}