Codeforces Round #587 (Div. 3)

题目链接：https://codeforces.com/contest/1216/problem

C. White Sheet

题解&代码：https://blog.csdn.net/qq_43381887/article/details/101165751

E2 Numerical Sequence (hard version)（二分/模拟）

题意：给定一个序列1 12 123 1234 … 求第k位的值， 1 < = k < = 1 e 18 1