# [Factor], <s>39 31</s> 43 bytes

    [ 0 -rot [ + + 10 /mod ] 2map swap suffix ]

[Factor]: https://factorcode.org/

[Try it online!](https://tio.run/##S0tMLskv@h8a7OnnbqWQm1iSoZCdWpSXmqNQnFpYmpqXnFqsUFCUWlJSWVCUmVeiYM3FVa1gCYS1MPp/tIKBgm5RfolCtII2EBoaKOjn5qcoxCoY5SYWKBSXg4jStLTMCoXY/8mJOTkKev8B "Factor – Try It Online")

Non-builtin counterpart to the `+` answer. Takes two reversed, padded lists of digits as input and outputs the reversed answer as a list of digits.