program collection (input,output);

const

   MAXCELLS= 50;
   MAXPTR = 2;
   EMPTYPTR = 0;

var

   graph: array[1..MAXCELLS,1..MAXPTR] of integer;
   mark: array[1..MAXCELLS] of boolean;
   numCells: integer;

procedure readCells;
var
  i, p, fromCell, ptr, toCell: integer;
begin
   readln(numCells);

   for i := 1 to numCells do begin
      for p := 1 to MAXPTR do begin
	     graph[i,MAXPTR] := EMPTYPTR;
      end;
    end;

   readln(fromCell, ptr, toCell);
   while (fromCell <> 0) do begin
       graph[fromCell,ptr] := toCell;
       readln(fromCell, ptr, toCell);
   end;
end;

procedure markCell(cell : integer);
var
   i, dest : integer;
begin
   for i := 1 to MAXPTR do begin
       dest := graph[cell,i];
       if (dest <> EMPTYPTR) and (mark[dest] = false) then begin
           mark[dest] := true;
           markCell(dest);
       end;
    end;
end;

procedure findReachable;
var
   i:integer;
begin
   mark[1] := true;
   for i := 2 to numCells do begin
      mark[i] := false;
   end;
   markCell(1);
end;

procedure printGarbage;
var
   i:integer;
begin
   write('Garbage cells: ');
   for i := 2 to numCells do begin
      if mark[i] = false then begin
         write(i:3);
      end;
   end;
   writeln;
end;

begin
   readCells;
   findReachable;
   printGarbage;
end.