import java.util.Scanner;

class Main{
    public static void main(String[] args){
        int H,W;
    	//?¨??????\??????????????????????????§????????????
		Scanner scanner = new Scanner(System.in);
		
		while(true){
			H = scanner.nextInt();
			W = scanner.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();
		}
    	scanner.close();
    }
}