A14336 | Kavi on Pairing Duty
时间限制1s
内存限制256MB
通过 / 提交0/0
题目描述
Kavi has $2n$ points lying on the $OX$ axis, $i$ -th of which is located at $x = i$ .
Kavi considers all ways to split these $2n$ points into $n$ pairs. Among those, he is interested in good pairings, which are defined as follows:
Consider $n$ segments with ends at the points in correspondent pairs. The pairing is called good, if for every $2$ different segments $A$ and $B$ among those, at least one of the following holds:
- One of the segments $A$ and $B$ lies completely inside the other.
- $A$ and $B$ have the same length.
Consider the following example:
 $A$ is a good pairing since the red segment lies completely inside the blue segment.
$B$ is a good pairing since the red and the blue segment have the same length.
$C$ is not a good pairing since none of the red or blue segments lies inside the other, neither do they have the same size.
Kavi is interested in the number of good pairings, so he wants you to find it for him. As the result can be large, find this number modulo $998244353$ .
Two pairings are called different, if some two points are in one pair in some pairing and in different pairs in another.
Kavi considers all ways to split these $2n$ points into $n$ pairs. Among those, he is interested in good pairings, which are defined as follows:
Consider $n$ segments with ends at the points in correspondent pairs. The pairing is called good, if for every $2$ different segments $A$ and $B$ among those, at least one of the following holds:
- One of the segments $A$ and $B$ lies completely inside the other.
- $A$ and $B$ have the same length.
Consider the following example:
 $A$ is a good pairing since the red segment lies completely inside the blue segment.
$B$ is a good pairing since the red and the blue segment have the same length.
$C$ is not a good pairing since none of the red or blue segments lies inside the other, neither do they have the same size.
Kavi is interested in the number of good pairings, so he wants you to find it for him. As the result can be large, find this number modulo $998244353$ .
Two pairings are called different, if some two points are in one pair in some pairing and in different pairs in another.
输入格式
The single line of the input contains a single integer $n$ $(1\le n \le 10^6)$ .
输出格式
Print the number of good pairings modulo $998244353$ .
输入输出样例
输入 #1
1
输出 #1
1
输入 #2
2
输出 #2
3
输入 #3
3
输出 #3
6
输入 #4
100
输出 #4
688750769
The good pairings for the second example are:
In the third example, the good pairings are:

In the third example, the good pairings are:

C++ 编辑器
输入
输出
可保存默认模板;新题优先使用已保存模板。
当前快捷键仅展示,暂不支持修改。
- 撤销
Ctrl / ⌘ + Z - 重做
Ctrl / ⌘ + Y - 查找
Ctrl / ⌘ + F - 全选
Ctrl / ⌘ + A - 复制
Ctrl / ⌘ + C - 剪切
Ctrl / ⌘ + X - 粘贴
Ctrl / ⌘ + V - 自动排版
工具栏排版按钮 - 草稿保存
编辑时自动保存到本机
历史
提交记录
状态说明时间源码
AI
作答助手
你好,我是作答助手。可以问思路、复杂度、样例含义或代码报错原因;不会直接给出完整 AC 代码。
确定要清空代码吗?
提交通过
评测结果:Accepted