Codeforces Round 698 B 题解

## Nezzar and Lucky Number

Nezzar's favorite digit among $1,…,9$ is $d$. He calls a positive integer lucky if $d$ occurs at least once in its decimal representation.

Codeforces Round 698 A 题解

## Nezzar and Colorful Balls

Nezzar has $n$ balls, numbered with integers $1,2,…,n$. Numbers $a_1,a_2,…,a_n$ are written on them, respectively. Numbers on those balls form a non-decreasing sequence, which means that $a_i≤a_{i+1}$ for all $1≤i<n$.

Codeforces Round 697 B 题解

## New Year's Number

Polycarp remembered the $2020$-th year, and he is happy with the arrival of the new $2021$-th year. To remember such a wonderful moment, Polycarp wants to represent the number $n$ as the sum of a certain number of $2020$ and a certain number of $2021$.

Codeforces Round 697 A 题解

## Odd Divisor

You are given an integer $n$. Check if $n$ has an odd divisor, greater than one (does there exist such a number $x$ ($x>1$) that $n$ is divisible by $x$ and $x$ is odd).

PTA 拯救007 题解