import java.util.Scanner;

public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int w = sc.nextInt();
		int h = sc.nextInt();
		String c = sc.next();
		String tmp = new String(c);
		sc.close();
		for(int i = 0; i < h; i++){
			for(int j = 0; j < w; j++){
				System.out.print(c);
				c = next(c);
			}
			c =  tmp = next(tmp);
			System.out.println();
		}
	}
	public static String next(String c){
		if(c.equals("B")){
			return "W";
		}else{
			return "B";
		}
	}
}