import java.io.*;
public class Main {
	public static void main(String[] args)throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
		int count = 0;
		
		while(true){
			//int count= 0;
			
			String[] str = br.readLine().split(" ");
			int H = Integer.parseInt(str[0]);
			int W = Integer.parseInt(str[1]);
			if(H==0 && W==0) break;
			
			
			//if(H%2 == 0){
				for(int i=0; i<H; i++){
					for(int j=0; j<W; j++){
						if((j+i)%2 == 0){
							System.out.print("#");
						}else {
							System.out.print(".");
						}
						
					}
					System.out.print("\n");
			
				}
				System.out.print("\n");
			
					
		}
		
	}
}
/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