use Memoize;
memoize("Ack");
my $count = 0;
sub Ack {
    $count++;
    return $_[0] ? ($_[1] ? Ack($_[0]-1, Ack($_[0], $_[1]-1))
    : Ack($_[0]-1, 1)) : $_[1]+1;
}

my $NUM = $ARGV[0];
$NUM = 1 if ($NUM < 1);
my $ack = Ack(3, $NUM);
print "Ack(3,$NUM): $ack";
#print times;
print "Ack() called $count times";