import java.util.Scanner;

class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		
		while(true){
			int H = sc.nextInt();
			int W = sc.nextInt();
			
			if(H==0&&W==0) break;
			
			for(int i=0;i<H;i++){
				for(int j=0;j<W;j++){
					if((i+j)%2==0){
						System.out.print("#");
					}else{
						System.out.print(".");
					}
					
				}
				
				System.out.println("");
			}
			System.out.println("");
		}
	}

}

