Description

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.

Input Format

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 Format

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

2 4
2 2

XX..XX..
XX..XX..
..XX..XX
..XX..XX

5 5
2 3

XXX...XXX...XXX
XXX...XXX...XXX
...XXX...XXX...
...XXX...XXX...
XXX...XXX...XXX
XXX...XXX...XXX
...XXX...XXX...
...XXX...XXX...
XXX...XXX...XXX
XXX...XXX...XXX

Hint

【Constraints】

For all testdata, $1\leqslant r,c,a,b\leqslant 10$.

【Source】

This problem is from COCI 2012-2013 CONTEST 3 T1 SAHOVNICA. Following the original testdata configuration, the full score is 50 points.

Translated and organized by Eason_AC.

Translated by ChatGPT 5