sub f{
#23456789 123456789 123456789 123456789 123456789 123456789 
$_=1x$_[0];for$n(1..sqrt$_[0]){m[^.{$n}.]g;s[\G(.{$n}).][${1}0]g;}
}
f(pop);
++$i and $1 and print $i while m[(.)]g;