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