luke20.pl

my %sets = ();

sub check {
  my ($x, $y) = @{$_[0]};
  return if (exists $sets{$x.','.$y} || (eval join "+", (abs $x . abs $y)=~/./g) > 19);
  
  $sets{$x.','.$y} = 1;
  check($_) foreach ([$x + 1, $y], [$x - 1, $y], [$x, $y + 1], [$x, $y - 1]);
}

check([0, 0]);
print scalar keys %sets;