program nikos(input,output);
uses crt;

 type
   pp=^rec;
    rec=record
     k1,k2,k3:integer;
     n,p:pp;
 end;

 var h,t,aux,temp:pp;
     c:char;
procedure insert(var x,y:pp);
var temp:pp;
 begin
  new(temp);
  write(' NEW RECORD: key1,key2,key3 =');
  readln(temp^.k1,temp^.k2,temp^.k3);

  if (x=nil) then
   begin
    x:=temp;
    y:=temp;
    x^.p:=nil;
    y^.n:=nil;
   end;

  if (x<>nil) then
   begin
    if temp^.k1<x^.k1 then
     begin
      temp^.n:=x;
      x^.p:=temp;
      x:=temp;
      x^.p:=nil;
    end;

    if temp^.k1>y^.k1 then
     begin
      temp^.p:=y;
      y^.n:=temp;
      y:=temp;

     end;

     if (temp^.k1>x^.k1) and (temp^.k1<y^.k1) then
      begin
       aux:=x;
        while (aux^.k1<temp^.k1) do aux:=aux^.n;
         temp^.n:=aux;
         temp^.p:=aux^.p;
         aux^.p^.n:=temp;
         aux^.p:=temp;
      end;
   end;
end;
procedure delete(var x,y:pp);
 begin
  if (x=nil) then writeln('nothing to delete');
   if (x<>nil) then
   begin
    writeln('Insert key1 that you want to delete :');
    readln(temp^.k1);

     if(x=y) and (temp^.k1=x^.k1) then
     begin;
     x:=nil;
     y:=nil;
     end;

     if(x<>y) and (temp^.k1=x^.k1) then
     begin
     temp:=x;
     x:=x^.n;
     dispose(temp);
     end;
     if (x<>y) and (temp^.k1=y^.k1) then
     begin;
     temp:=y;
     y^.p^.n:=nil;
     y:=y^.p;
     dispose(temp);
     end;

     if (temp^.k1>x^.k1) and (temp^.k1<y^.k1) then
     begin
     aux:=x;
     while(aux^.k1<>temp^.k1) do aux:=aux^.n;
     writeln(aux^.k1);
     aux^.n^.p:=aux^.p;
     aux^.p^.n:=aux^.n;
     dispose(aux);
     end;
end;
end;
procedure print(x,y:pp);
var aux:pp;
begin
  aux:=x;
  if x=nil then writeln('EMPTY');
  if aux<>nil then
   begin
    while (aux<>y) do
     begin
      writeln('key1:',aux^.k1,'  key2:',aux^.k2,'  key3:',aux^.k3);
      aux:=aux^.n
     end;
    writeln('key1:',aux^.k1,'  key2:',aux^.k2,'  key3:',aux^.k3);
  end;
end;

begin
 clrscr;
 h:=nil;
 if(h=nil) then writeln('to h einai keno');
 t:=nil;
 c:='g';
 if t=nil then writeln('to t einai keno');

  while(c<>'q') do
   begin
    writeln('<i>insert   <d>elete   <p>rint   <q>uit');
    readln(c);
    if c='i' then insert(h,t);
    if c='p' then print(h,t);
    if c='d' then delete(h,t);
   end;
end.