def q2p(phred_Sanger_Quality_score):
    """Quality [score] to probability (q2p)
    converter.
    
    Args:
        phred_Sanger_Quality_score (str): Input Q-Score as single-character string
    
    Returns:
        int: Output Q-Score as multi-character decimal probability.
    """
    Q = ord(phred_Sanger_Quality_score) - 33
    return round(10 ** (-Q / 10), 8)