begin 
    procedure a0;
        begin 
        procedure a1;
            begin 
            procedure a2;
                begin 
                procedure a3;
                    begin 
                    procedure a4;
                        begin 
                        procedure a5;
                            begin 

                            end;

                        ;
                        end;

                    ;
                    end;

                ;
                end;

            ;
            end;

        ;
        end;

    ;
end