import re


def make_strike_tags(line: str) -> str:
    """Find strike marks in string and replace them with <s> tags."""
    return re.sub(
        r"""
            (?<![\w-]) 
            (--) 
            (?![<>\s-]) 
            ([^<>]+?) 
            (?<![<>\s-]) 
            \1 
            (?![\w-])
        """,
        r'<s>\2</s>',
        line,
        flags=re.X
    )