program queue3(input,output);
type
    list=^node;
    node=record
          elem: integer;
          next: list
         end;
    queue=record
            start: list;
            fin: list
          end;

procedure init(var q: queue);
  begin
      q.start:=nil;
      q.fin:=nil
  end;

function isempty(var q: queue): boolean;
  begin
    isempty:=q.start=nil;
  end;

procedure pushQ(var q: queue; e: integer);
var p: list;
  begin
    new(p);
    p^.elem:=e;
    p^.next:=nil;
    with q do
      begin
        if(start=nil) then
          start:=p
        else
          fin^.next:=p;
        fin:=p;
      end;
  end;

procedure popQ(var q: queue; e: integer);
var p: list;
  begin
   if(isempty(q)) then
    write('error')
   else
    begin
      e:=q.start^.elem;
      p:=q.start;
      q.start:=q.start^.next;
      dispose(p);
      if(q.start=nil) then q.fin:=nil;
    end;
  end;

var f: file of integer;
    c,d: integer;
    och: queue;
begin
  assign(f,'input.txt');
  read(c);
  rewrite(f);
  while(c<>0) do
    begin
      if(c<0) then
        write(f,c)
      else
        pushQ(och,c);
      read(c);
    end;
  reset(f);
  while(not(eof(f))) do
    begin
      read(f,d);
      write(d,' ');
    end;
  while(not(isempty(och))) do
    begin
      popQ(och,c);
      write(c,' ');
    end;
end.