from pathlib import Path


def get_audio_path(audio_dir, song_id):
    """
    Return the path to the mp3 given the directory where the audio is stored
    and the Song ID.

    Args:
        audio_dir (String): The directory where the audio is stored.
        song_id (String): The Song ID.

    Returns:
        String: The path to the mp3 file with the given song ID.
    """
    return Path(audio_dir) / (str(song_id) + '.mp3')