var  f:text;
     s1,s2:array[0..1024] of integer;
     a:array[0..1024,0..1024] of byte;
     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]);
for j:=1 to m do
 if (a[n,j]>0) and (a[n,j]>r) then
  begin
   r:=a[n,j];
   write(f,s2[j],' ');
  end;
close(f);
end.