uses Crt;
const imax=12;
type pt=^klon;
     klon=record
            r: real;
            ptl, ptr: pt;
          end;
var koren: pt;
    i: integer;

procedure create(var ptt:pt);
var ir: integer;
begin
   new(ptt);
   i:=i+1;
   ptt^.r:=i;
   ptt^.ptl:=nil;   ptt^.ptr:=nil;
   if i<imax then
   begin
      ir:=random(2);
      if ir in [0,1] then
      begin
         write(ptt^.r:4:0,'+l',i);  create(ptt^.ptl);
      end else write(ptt^.r:4:0,'-l',i);
      if ir in [1,2] then
      begin
         write(ptt^.r:4:0,'+r',i);  create(ptt^.ptr);
      end else write(ptt^.r:4:0,'-r',i);
   end;
end;

procedure go(var ptt:pt);
var rle, rri: real;
    le, ri: pt;
begin
   le:=ptt^.ptl; ri:=ptt^.ptr;
   if ri=nil then rri:=0 else rri:=ri^.r;
   if le=nil then rle:=0 else rle:=le^.r;
   writeln(rle:3:0,'<--',ptt^.r:3:0,' -->',rri:3:0);
   if ptt^.ptr<>nil then go(ptt^.ptr);
   if ptt^.ptl<>nil then go(ptt^.ptl);
end;

begin
   ClrScr;
   randomize;
   i:=0;
   create(koren);
   writeln; writeln;
   go(koren);
end.