def get_good_region(index, seq_count, arg):
    """
    Return regions marked for finding primers. Because of alignment gap, PCR
    product may smaller than given length limitation.
    """
    n = arg.max_product - arg.min_product
    good_region = set()
    for i, j in zip(index, seq_count):
        if j >= arg.resolution:
            good_region.update(range(i - arg.max_primer, i - n))
            good_region.update(range(i + arg.min_product, i - arg.
                max_primer + arg.max_product))
    return good_region
