I grip my troubles within my hand, then hurl them off a thousand lands.— SHUN, ONMYWAY
Consider that Simons is given an array $a$ of size $m$.
Simons must operate on the array exactly once as follows:
- First, he has to select an integer
$k$and choose$k$pairs of integers$[l_1,r_1],[l_2,r_2],\ldots,[l_k,r_k]$, such that: $l_i\le r_i$for each$1\le i\le k$,$l_1=1$,$r_k=m$, and$r_i+1=l_{i+1}$for each$i$from$1$to$k-1$.
- Then, he reverses each subarray
$[a_{l_i},a_{l_i+1},\ldots, a_{r_i}]$independently. After this, the array will become$[a_{r_1},a_{r_1-1},\ldots,a_{l_1},a_{r_2},\ldots,a_{l_{k-1}},a_{r_{k}},a_{r_k-1},\ldots,a_{l_k}]$.
You are given an array $T$ of size $n$. Count the number of arrays $S$ such that Simons can transform $S$ to $T$, modulo $998\,244\,353$.
Input
Each test contains multiple test cases. The first line contains the number of test cases $t$ ($1 \le t \le 8000$). The description of the test cases follows.
The first line contains an integer $n$ ($1\le n\le 8000$) — the length of $T$.
The second line contains $n$ integers $T_1,T_2,\ldots,T_n$ ($1\le T_i\le 8000$) — the elements of $T$.
It is guaranteed that the sum of $n$ over all test cases does not exceed $8000$.
Output
For each test case, output a single integer — the number of arrays $S$, modulo $998\,244\,353$.
Note
In the first test case, we can see only the following arrays can be transformed to $T$:
- For
$S=[2,1,1,1]$, Simons will choose$[1,3]$and$[4,4]$. Thus, the array will become$[1,1,2,1]$, equal to$T$. - For
$S=[1,2,1,1]$, Simons will choose$[1,4]$. - For
$S=[1,1,2,1]$, Simons will choose$[1,2]$,$[3,3]$, and$[4,4]$. - For
$S=[1,1,1,2]$, Simons will choose$[1,2]$and$[3,4]$.
In the second test case, we can see only the following arrays can be transformed to $T$:
- For
$S=[1,1,3,2]$, Simons will choose$[1,1]$and$[2,4]$. - For
$S=[1,2,1,3]$, Simons will choose$[1,1]$,$[2,2]$, and$[3,4]$. - For
$S=[1,2,3,1]$, Simons will choose$[1,1]$,$[2,2]$,$[3,3]$, and$[4,4]$. - For
$S=[1,3,2,1]$, Simons will choose$[1,4]$. - For
$S=[2,1,1,3]$, Simons will choose$[1,2]$and$[3,4]$. - For
$S=[2,1,3,1]$, Simons will choose$[1,2]$,$[3,3]$, and$[4,4]$. - For
$S=[3,2,1,1]$, Simons will choose$[1,3]$and$[4,4]$.
样例
5
4
1 1 2 1
4
1 2 3 1
6
1 3 2 3 3 2
10
2 3 1 4 3 1 4 3 1 2
1
8000
4
7
22
383
1
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