P7754 [COCI 2012/2013 #3] SAHOVNICA

Mirko has become a hardcore patriot, so he asks you to draw a Croatian chessboard for him.

A chessboard consists of red squares and white squares. The top-left square of the chessboard is red. The remaining squares alternate between white and red across the board. In this problem, we use `X` to represent a red area and `.` to represent a white area. Mirko's chessboard should consist of $r\times c$ squares, and each square is an $a\times b$ character matrix made up of the characters `X` and `.`. Please help him draw this chessboard.

The input consists of two lines. The first line contains two integers $r,c$, representing the number of rows and columns of the chessboard, respectively. The second line contains two integers $a,b$, representing the number of rows and columns of the character matrix in each square, respectively.

Output a total of $r\times a$ lines, each containing $c\times b$ characters, describing the final drawn chessboard.

**【Constraints】** For all testdata, $1\leqslant r,c,a,b\leqslant 10$. **【Source】** This problem is from **_[COCI 2012-2013](https://hsin.hr/coci/archive/2012_2013/) [CONTEST 3](https://hsin.hr/coci/archive/2012_2013/contest3_tasks.pdf) T1 SAHOVNICA_**. Following the original testdata configuration, the full score is 50 points. Translated and organized by [Eason_AC](https://www.luogu.com.cn/user/112917). Translated by ChatGPT 5