2019 acm-icpc银川站F.Function!(数学分块)
给你一个式子∑a=2n(a∑b=an⌊fa−1(b)⌋⌈fb−1(a)⌉)\sum_{a=2}^n{\left( a \sum_{b=a}^n{\lfloor f_{a}^{-1}\left( b \right) \rfloor}\lceil f_{b}^{-1}\left( a \right) \rceil \right)}∑a=2n(a∑b=an⌊fa−1(b)⌋⌈fb−1(a)⌉)让...
