import io

def sanitize_filename(s: str) -> str:
    return '.'.join([sanitize_filename_part(p) for p in s.split('.')])

def sanitize_filename_part(s: str) -> str:
    alnum_or_space = ''.join([c if c.isalnum() else ' ' for c in s])
    return '-'.join(alnum_or_space.split())