$n=<>;@a=glob<>;
open(t,">/tmp/t");

sub f{
	my($x,$u)=@_;
	if(!$h{$x}++){
		if(!$u){
			print t $x,$/;
		}else{
			for$i(0..$n-1){
				if($u&1<<$i){
					my$y=$a[$i];
					f($x.$y,$u^1<<$i);
				}
			}
		}
	}
}
f('',(1<<$n)-1);

open(p,"sort -nr /tmp/t|factor|");
($r)=(grep(!/\d /,<p>),-1);
print $r+0;