Tell them you enjoyed your time with them (even if you didn't) and you look forward to the next round of interviews as a further opportunity to explain your value to their company in further detail.

告诉你与他们度过了美好珍贵的时光(即使你不这么认为)，然后期待下一轮的面试，以此作为进一步阐述本人对公司价值的机会。