import java.util.Scanner;
class N082{
	public static void main(String args[]){
		Scanner s = new Scanner(System.in);
		int w = s.nextInt();
		int h = s.nextInt();
		String a = s.next();
		String b;
		for(int i = 0; i < h; i++){
			b = a.equals("B") ? "W" : "B";
			for(int j = 0; j < w / 2; j++){
				System.out.print(a+b);
			}
			if(w % 2 != 0){
				System.out.println(a);
			}else{
				System.out.println();
			}
			a = b;
		}
	}
}