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Time Limit: 1 s Memory Limit: 512 MB Total points: 100

#13471. Permutation

الإحصائيات

给出 $n,P$,设

$$ f_n = \left(\sum_{p\text{ is a permutation of length }n} [\exists i \in [1,n] , p_i = i][\exists i \in [1,n] , p_i = n - i + 1]\right) \bmod\ P $$

你需要求出 $\bigoplus_{i=1}^n f_i$ 的值。

输入格式

输入一行两个整数 $n,P$。

输出格式

一行一个整数表示答案。

样例数据

样例输入

2 100000

样例输出

1

样例解释

$n=1$ 时排列 $(1)$ 满足上述两个条件,故 $f_1 = 1$;

$n=2$ 时排列 $(1,2),(2,1)$ 均有一个条件不满足,故 $f_2 = 0$;

所以答案为 $1\oplus 0 = 1$。

子任务

对于 $100\%$ 的数据,$1 \leq n \leq 10^7 , n + 1 \leq P \leq 10^9$。

测试点编号 $n \leq$ $P$
$1$ $18$ 无特殊限制
$2$ $60$
$3$ $300$
$4$ $1000$ $=998244353$
$5$ $5000$
$6$ $3 \times 10^4$
$7$ $10^5$
$8$ $3 \times 10^5$
$9$ $5 \times 10^5$
$10$ $1000$ 是质数
$11$ $10^4$
$12$ $10^5$
$13$ $10^6$
$14$ $10^7$
$15$ $5000$ 无特殊限制
$16$ $3 \times 10^4$
$17$ $10^5$
$18$ $5 \times 10^5$
$19$ $2 \times 10^6$
$20$ $10^7$

Editorials

IDTypeStatusTitlePosted ByLast UpdatedActions
#847EditorialOpen题解alpha10222026-01-28 02:20:46View

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