[2019HDU多校第一场][HDU 6588][K. Function]

题目链接：http://acm.hdu.edu.cn/showproblem.php?pid=6588 题目大意：求\(\sum_{i=1}^{n}gcd(\left \lfloor \sqrt[3]{i} \right \rfloor,i),\ n\leq 10^{21}\) 题解：考虑对\(\l