from typing import List


def simple_acronym_detection(s: int, i: int, words: List[str], *args) -> int:
    """Detect acronyms based on runs of upper-case letters.

    Arguments:
        s (int): Index of first letter in run
        i (int): Index of current word
        words (list of str): Segmented input string
        args: Placeholder to conform to signature of
            advanced_acronym_detection

    Returns:
        int: Index of last letter in run
    """
    # Combine each letter into a single string.
    acr_str = "".join(words[s:i])

    # Remove original letters in word list.
    for _ in range(s, i):
        del words[s]

    # Replace them with new word grouping.
    words.insert(s, "".join(acr_str))

    return s