program ex;
type
 ss=array[1..1000]of boolean;
var
 a:ss;
 f1,f2:text;
 i:integer;
 n,max,m,x:integer;
procedure init;
 var
  i:integer;
 begin
  assign(f1,'random.in');
  assign(f2,'random.out');
  reset(f1);
  rewrite(f2);
  readln(f1,n);
  max:=0;
  for i:=1 to n do
   begin
     read(f1,x);
     if x>max then max:=x;
     a[x]:=true;
   end;
 end;
procedure print;
 var
  i:integer;
 begin
  m:=0;
  for i:=1 to max do
   if a[i]=true then inc(m);
  writeln(f2,m);
  for i:=1 to max do
   if a[i]=true then write(f2,i,' ');
 end;
begin
 init;
 print;
 close(f1);
 close(f2);
end.