P10172 "OICon-02" Pick Stone

Little S has an $n\times m$ chessboard. Initially, each cell has a stone. Each time, Little S may remove one stone such that the number of removed stones around it (4-neighborhood) is at most $1$. Find the maximum number of stones Little S can remove, and construct one valid removing plan.

One line with two positive integers $n, m$, representing the board size.

The first line contains one positive integer, the maximum number of stones that can be removed, $ans$. Then output $n$ lines, each with $m$ integers between $-1$ and $ans$. The number in each cell indicates at which step the stone in this cell is removed. If the stone in that cell is not removed, output $-1$.

### Sample Explanation For Sample $1$, when removing $(1,1)$, there are $0$ removed cells around it. When removing $(1,2)$ and $(2,1)$, there is $1$ removed cell around each of them. Therefore, the construction satisfies the requirement. It is easy to prove that there is no better answer. ### Constraints **This problem uses bundled testdata.** | $\text{Subtask}$ | Special Property | $\text{Score}$ | |:--:|:--:|:--:| | $1$ | $n=1$ | $20$ | | $2$ | $n=2$ | $30$ | | $3$ | $n=3$ | $50$ | For $100\%$ of the testdata: $\bm{1\leq n\leq3}$, $1\leq m\leq10^5$. If you get the first part (the maximum number of stones that can be removed) correct but fail to construct correctly, you will get $70\%$ of the score. For each subtask, your score is the minimum score among all test points in that subtask. Note that you still need to output $n\times m$ numbers as the construction plan in the required format. We recommend outputting all $-1$. It is guaranteed that `checker.cpp` runs in no more than $0.5$ seconds with an output that meets the format requirements. Translated by ChatGPT 5