def penalize_short(genotype, weight=20):
    """fitness function handling short notes
    
    Args:
        genotype ((int, int)[]): list of tuples (pitch, dur) representing genotype of a chromosome
        weight (int, optional): Defaults at 20.  Defines penalty/reward rate
    
    Returns:
        int: aggregate fitness value based on short notes
    """
    total = 0
    for i, (ed, dur) in enumerate(genotype):
        if dur < 4:
            total += weight * -1
    return total