Program tz;
Var
   n,k,i:integer;f1,f2:text;
   a:array [1..100] of integer;

procedure Tsort(q:integer);
Var
   temp:array [1..1000] of boolean;
   i,j:integer;
Begin
   k:=0;
   fillchar(temp,sizeof(temp),false);

   For i:=1 to q do
     temp[a[i]]:=true;

   fillchar(a,sizeof(a),0);
   For i:=1 to 1000 do
     if temp[i] then
        Begin
          inc(k);
          a[k]:=i;
        End;
End;
Begin
   assign(f1,'random.in');
   assign(f2,'random.out');
   reset(f1);rewrite(f2);
   readln(f1,n);
   For i:=1 to n do read(f1,a[i]);
   tsort(n);
   writeln(f2,k);
   For i:=1 to k-1 do write(f2,a[i],' ');
   writeln(f2,a[k]);
   close(f1);close(f2);
End.