import java.util.*;

class Main{
	public static void main(String args[]){
		int H, W;
		Scanner scan = new Scanner(System.in);

		while(true){
			H = scan.nextInt();
			W = scan.nextInt();
			
			if(H == 0 && W == 0){break;}

			for(int i=0; i<H; i++){
				for(int k=0; k<W; k++){
					if(i % 2 == 0){
						//??¶??°????????????
						if(k % 2 ==0){
							System.out.print("#");
						}
						else{
							System.out.print(".");
						}
					}
					else{
						//?\???°????????????
						if(k % 2 ==0){
							System.out.print(".");
						}
						else{
							System.out.print("#");
						}
					}
				}
				System.out.println("");
			}
			System.out.println("");
		}
	}
}
/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