const
  maxnum=10010;
type
  tdata=array[0..maxnum] of boolean;
var
  data:tdata;
  n,i,x,vans:longint;

begin
  assign(input,'random.in');
  reset(input);
  assign(output,'random.out');
  rewrite(output);
  readln(n);
  fillchar(data,sizeof(data),false);
  vans:=0;
  for i:=1 to n do
    begin
      read(x);
      if (not(data[x])) then
        begin
          inc(vans);
          data[x]:=true;
        end;
    end;

  writeln(vans);
  for i:=1 to maxnum do
    if (data[i]) then
      write(i,' ');
  writeln;

  close(input);
  close(output);
end.