P6687 How to Master Excel Spreadsheets

There is a $2 \times n$ table, filled with the numbers $1 \sim 2 \times n$ with no repetition and nothing missing. You may perform several operations. In each operation, you can choose a $2 \times 2$ square area and then rotate it by $180\degree$. Given the current state and the target state, determine whether the target state can be reached. If it can, output the minimum number of operations.

The first line contains a positive integer $n$. The next two lines each contain $n$ positive integers, describing the current state of the table. The next two lines each contain $n$ positive integers, describing the target state of the table.

If there is no solution, output one line `dldsgay!!1`. Otherwise, output one integer, the minimum number of operations.

#### Subtasks This problem uses bundled testdata. For $100\%$ of the testdata: $1 \leq n \leq 10^6$. This problem has $10$ subtasks. The score and constraints of each subtask are as follows: Subtask $1$ ($1$ point): It is guaranteed that the output must be `dldsgay!!1`. Subtask $2$ ($1$ point): It is guaranteed that the target state is the same as the current state. Subtask $3$ ($4$ points): $n = 1$. Subtask $4$ ($5$ points): $n = 2$. Subtask $5$ ($14$ points): $1 \leq n \leq 20$. Subtask $6$ ($19$ points): $1 \leq n \leq 100$. Subtask $7$ ($19$ points): $1 \leq n \leq 1000$. Subtask $8$ ($8$ points): It is guaranteed that the first row of the target state is $1 \sim n$ in order, and the second row is $n + 1 \sim 2n$ in order. Subtask $9$ ($10$ points): It is guaranteed that there is no unsolvable case. Subtask $10$ ($19$ points): No special constraints. Translated by ChatGPT 5