($K,$N)=@_=<>;
map{//;$_[$_+=$']=1while$_<$N}2..$N;
@p=grep!$_[$_],$K..$N;
for(@p){
	$h=$_;
	while($h>9){
		$t=0;
		$t+=$_ for$h=~/./g;
		$h=$t
	}
	if($l<=$h[$h]){
		$l=$h[$h]+1
	}
	$h[$h]=++$r;
	if($r-$l+1>=$x){
		$x=$r-$l+1;
		$\=$p[$l-1]
	}
}
print