from typing import List
import string


def format_int_alpha(value: int) -> str:
    """Format a number as lowercase letters a-z, aa-zz, etc."""

    assert value > 0
    result: List[str] = []

    while value != 0:
        value, remainder = divmod(value - 1, len(string.ascii_lowercase))
        result.append(string.ascii_lowercase[remainder])

    result.reverse()
    return "".join(result)