program cojs74;
var
  a:array[0..1010] of longint;
  i,j,k,m,n:longint;
begin
  assign(input,'random.in');
  assign(output,'random.out');
  reset(input);
  rewrite(output);
 
  fillchar(a,sizeof(a),0);
  readln(n);
  m:=0;
  for i:=1 to n do
    begin
       read(k);
       if a[k]=0 then inc(m);
       a[k]:=1;
    end;
  writeln(m);
  for i:=1 to 1000 do
    if a[i]<>0 then
      write(i,' ');
   writeln;
 
  close(input);
  close(output);
end.