# include <stdio.h>
long int l,i,j,k,n,a[1000];
int main ()
{
freopen ("nrtri.in","r",stdin);
freopen ("nrtri.out","w",stdout);
scanf ("%li",&n);
for (i=0;i<n;i++)
scanf ("%li",&a[i]);
for (i=0;i<n-2;i++)
for (j=i+1;j<n-1;j++)
for (k=j+1;k<n;k++)
{
if (a[i]<=a[j]+a[k])
if (a[j]<=a[i]+a[k])
if (a[k]<=a[i]+a[j])
l++;
}
printf ("%li",l);
return 0;
}