var i,j,p,m,n:integer;
a,b,d:array[1..1024] of byte;
c:array[1..1024,1..1024] of byte;
f,g:text;
procedure citire(var m,n:integer);
var i,j:integer;
begin
readln(f,m,n);
for i:=1 to m do
read(f,a[i]);
for j:=1 to n do
read(f,b[j]);
readln(f);
end;
function max(n,m:integer):integer;
begin
if n>m then max:=n
else max:=m;
end;
begin
assign(f,'cmlsc.in'); reset(f);
assign(g,'cmlsc.out'); rewrite(g);
citire(m,n);
for i:=1 to m do
  for j:=1 to n do
     if a[i]=b[j]
      then c[i,j]:=1+c[i-1,j-1]
      else c[i,j]:=max(c[i-1,j],c[i,j-1]);
i:=m; j:=n;  p:=1;
while ((i>0) and (j>0)) do
 if a[i]=b[j]then begin
                     d[p]:=a[i];
                     dec(i);
                     dec(j);
                     inc(p);
                  end
 else if c[i-1,j]<c[i,j-1] then dec(j)
 else dec(i);
writeln(g,p-1);
for i:=p-1 downto 1 do
write(g,d[i],' ');
close(f); close(g);
end.