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حد الوقت: 1 s حد الذاكرة: 512 MB مجموع النقاط: 100

#13471. 排列

الإحصائيات

給定 $n,P$,設

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

你需要求出 $\bigoplus_{i=1}^n f_i$ 的值。

輸入格式

輸入一行兩個整數 $n,P$。

輸出格式

一行一個整數表示答案。

範例

範例輸入 1

2 100000

範例輸出 1

1

說明 1

$n=1$ 時排列 $(1)$ 滿足上述兩個條件,故 $f_1 = 1$;

$n=2$ 時排列 $(1,2),(2,1)$ 均有一個條件不滿足,故 $f_2 = 0$;

所以答案為 $1\oplus 0 = 1$。

子任務

對於 $100\%$ 的資料,$1 \leq n \leq 10^7 , n + 1 \leq P \leq 10^9$。

測試點編號 $n \leq$ $P$
1 18 無特殊限制
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 是質數
11 $10^4$
12 $10^5$
13 $10^6$
14 $10^7$
15 5000 無特殊限制
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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