program sss;
var a,b,rez:array[1..1024] of integer;
    v:array[0..1024,0..1024] of integer;
    n,m,i,ii,j,k:integer;
    f,g:text;
function max(a,b:integer):integer;
  begin
  if a>b then
    max:=a
    else
    max:=b;
  end;
begin
assign(f,'cmscl.in'); reset(f);
assign(g,'cmscl.out'); rewrite(g);
readln(f,m,n);
  for i:=1 to m do
    read(f,a[i]);
  for i:=1 to n do
    read(f,b[i]);
for i:=1 to m do
  for j:=1 to n do
    begin
      if a[i]=b[j] then
        v[i,j]:=v[i-1,j-1]+1
        else
        v[i,j]:=max(v[i-1,j],v[i,j-1]);
    end;
    writeln(g,v[m,n]);
    i:=m;
    j:=n;
     for k:=v[m,n] downto 1 do
       begin
         while v[i,j]=v[i-1,j] do
           i:=i-1;
         while v[i,j]=v[i,j-1] do
           j:=j-1;
         rez[k]:=a[i];
         i:=i-1;
       end;
       for i:=1 to v[m,n] do
         write(g,rez[i],' ');
close(f);
close(g);
end.