#1249. 不可做题1

You are given two sequences $a_1, a_2, \dots, a_n$ and $b_1, b_2, \dots, b_m$.

Two sequences $(x_1, x_2, \dots, x_p)$ and $(y_1, y_2, \dots, y_q)$ match iff $p = q$ and $x_i = x_j \Leftrightarrow y_i = y_j$ for every possible pair $1 \leq i, j \leq p$.

Output the number of subsequences of $a_1, a_2, \dots, a_n$ that match $b_1, b_2, \dots, b_m$.

The first line contains two integers $n$, $m$ ($1 \leq n \leq 3000$, $1 \leq m \leq \min(5,n)$).

The second line contains $n$ integers $a_1, a_2, \dots, a_n$ ($1 \leq a_i \leq n$).

The third line contains $m$ integers $b_1, b_2,\dots, b_m$ ($1 \leq b_i \leq m$).

Output one integer: the answer.

Good Luck!