type
  list=^node;
  node=record
        elem: integer;
        next: list;
       end;

procedure change(var L: list; E1,E2: integer);
var p: list;
  begin
    if(L<>nil) then
      begin
        if(L^.elem=E1) then L^.elem:=E2;
        change(L^.next,E1,E2);
      end;
  end;