def final_12wellplate(sample_number):
    """Determines well containing the final sample from sample number for 12 well plate spotting

    """
    letter_12wellplate = ['A', 'B', 'C']
    plate_number = sample_number// 12 + (1 if sample_number % 12 > 0 else 0)
    final_well_column = sample_number // 3 + \
        (1 if sample_number % 3 > 0 else 0) - ((plate_number-1) * 4)
    final_well_row = letter_12wellplate[sample_number - ((plate_number - 1) * 12)-(final_well_column*3) - 1]
    return final_well_row + str(final_well_column)