#include <stdio.h>
int i,j,l,n,nr,a[801];
int main()
{
    freopen("nrtri.in","r",stdin);
    freopen("nrtri.out","w",stdout);
    scanf("%d",&n);
    for(i=1;i<=n;i++)
     scanf("%d",&a[i]);
    for(i=1;i<=n;i++)
     for(j=i+1;j<=n;j++)
      for(l=j+1;l<=n;l++)
       if(a[i]+a[j]>=a[l])
       {
                     
        nr++;
        }
    printf("%d",nr);
    return 0;
}