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();
    }
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz