> **EDIT:** As specified in the comment it seems that I did not correctly understand the question (thank you @Glen Yates). Here is another method, it would be inspired on the same principle of usage of a [keypad](https://www.youtube.com/watch?v=yYnX5QodqQ4). [![enter image description here][4]][4] [1]: https://i.sstatic.net/TS0Dh.jpg [2]: https://i.sstatic.net/bw4Sb.jpg [3]: https://i.sstatic.net/s2vte.jpg [4]: https://i.sstatic.net/rQ4L4.jpg