How would you solve this 'interview' question in D?

[Andrej Mitrovic]

On 6/27/13, Andrej Mitrovic <andrej.mitrovich at gmail.com> wrote:
> On 6/27/13, H. S. Teoh <hsteoh at quickfur.ath.cx> wrote:
>> Well, it's still cheating, though. :-P I think the 4-cycle algorithm is
>> probably still the best one I've seen.
>
> What I don't understand is why the CPU is so slow that it takes ages
> to go through int.min .. int.max in a loop.
>

I mean this takes 31 seconds on my machine (obviously without
optimization flags):

-----
int f(int n) { return n; }

void main()
{
    foreach (n; int.min..int.max)
        f(f(n));
}
-----

Maybe I need an upgrade.