20130514 :: problem 9

type
    pnode = ^node;
    node = record
        s : string;
        left, right : pnode;
    end;

var
    ls, i : longint;
    ch : char;
    s : string;
    root : pnode;

    procedure tooLong();
    begin
        writeln('ERROR! Maximal string length is 6.');
        halt(0);
    end;

    procedure insert(cur : pnode; s : string);

    var
        tmp : pnode;

        function createNode(s : string) : pnode;
        begin
            new(tmp);
            tmp^.s := s;
            tmp^.left := nil;
            tmp^.right := nil;
            createNode := tmp;
        end;

    begin
        if (cur = nil) then begin
            root := createNode(s);
            exit;
        end;
        if (s < cur^.s) then begin
            if (cur^.left = nil) then cur^.left := createNode(s) else insert(cur^.left, s);
            exit;
        end;
        if (cur^.s < s) then begin
            if (cur^.right = nil) then cur^.right := createNode(s) else insert(cur^.right, s);
            exit;
        end;
    end;

    procedure printTree(cur : pnode);
    begin
        if (cur = nil) then exit;
        printTree(cur^.left);
        writeln(cur^.s);
        printTree(cur^.right);
        dispose(cur);
    end;

begin
    read(ch);
    s := '$$$$$$';
    root := nil;
    while (ch <> '.') do begin
        ls := 0;
        for i := 1 to 6 do
            s[i] := #0;
        if (ch = ',') then read(ch);
        while (ch <> '.') and (ch <> ',') do begin
            inc(ls);
            if (ls > 6) then tooLong();
            s[ls] := ch;
            read(ch);
        end;
        insert(root, s);
    end;
    printTree(root);
end.