var  f:text;
     s1,s2,sol:array[0..1024] of integer;
     a:array[0..1024,0..1024] of integer;
     i,j,n,m,r:integer;
 begin
  assign(f,'cmlsc.in');
  reset(f);
  readln(f,n,m);
  for i:=1 to n do
   read(f,s1[i]);
  readln(f);
  for i:=1 to m do
   read(f,s2[i]);
  close(f);
  for i:=0 to n do
  for j:=0 to m do
   begin
     if (j=0) or (i=0) then
      a[i,j]:=0
      else
     if s1[i]=s2[j] then
      a[i,j]:=a[i-1,j-1]+1
      else
      if a[i-1,j]>=a[i,j-1] then
       a[i,j]:=a[i-1,j]
        else
       a[i,j]:=a[i,j-1];
    end;
 r:=0;
 assign(f,'cmlsc.out');
 rewrite(f);
 writeln(f,a[n,m]);
 i:=n;
 j:=m;
 while a[i,j]<>0 do
  begin
   if s1[i]=s2[j] then
    begin
     r:=r+1;
     sol[r]:=s1[i];
     i:=i-1;
     j:=j-1;
    end
   ELSE
    if a[i-1,j]>=a[i,j-1] then
     i:=i-1
      else
     j:=j-1;
  end;
 for i:=r downto 1 do
  write(f,sol[i],' ');
 close(f);
end.