[요약] 체커판을 출력해야합니다.

체커판은 빨간색 칸과 흰색 칸으로 이루어져있고 체스판처럼 인접한 칸의 색깔은 다른 색깔입니다. 또한 왼쪽 위 색깔은 언제나 빨간색입니다.

입력으로 체스판의 크기, 각 칸의 크기가 주어졌을 때 빨간색 칸은 X(대문자), 흰색 칸은 .(점) 으로 출력하세요.

The chessboard consists of red and white cells. The upper left cell is red, with the remaining cells alternating between white and red in rows as well as columns. We will represent red areas with ‘X’ (uppercase letter x) characters, and white areas with ‘.’ (period) characters.

Mirko's chessboard should consist of R × C cells, that is, R rows and C columns. Each row should be A characters high, and each column B characters wide. Consider the sample tests below for further clarification.

입력

• The first line of input contains two positive integers R and C (1 ≤ R, C ≤ 10) from the problem statement.
• The second line of input contains two positive integers A and B (1 ≤ A, B ≤ 10) from the problem statement.

출력

입출력 예

입력

2 4
2 2

출력

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

입력

5 5
2 3

출력

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

출처:coci/2012-2013/contest3/1 번
요약:ladown21