∑i=1n⌊aibi⌋\sum_{i=1}^n\lfloor \dfrac{a_i}{b_i}\rfloor∑i=1n⌊biai⌋ 是否等于 ⌊∑i=1naibi⌋\lfloor \sum_{i=1}^n \dfrac{a_i}{b_i} \rfloor⌊∑i=1nbiai⌋