from typing import List


def group(source: str) -> List[str]:
    """
    Transforms the input into a list where numbers are
    grouped as one element.
    """
    res = []
    i = 0
    n = len(source)
    while i < n:
        char = source[i]
        if not char.isdigit():
            res.append(char)
            i += 1
            continue

        i += 1
        while source[i].isdigit():
            char += source[i]
            i += 1

        res.append(char)

    return res