import io


def skiplines(s, prefix):
    """
    Skip lines starting with prefix in s

    >>> skiplines('a\\nb\\na\\n', 'a')
    'b\\na\\n'
    >>> skiplines('a\\na\\n', 'a')
    ''
    >>> skiplines('', 'a')
    ''
    >>> skiplines('a\\nb', 'b')
    'a\\nb'
    """
    cs = io.StringIO(s)

    for line in cs:
        if not line.startswith(prefix):
            return line + cs.read()

    return ''