import java.util.Scanner;

public class Main {

    public static void main(String[] args) throws Exception {
        Scanner input = new Scanner(System.in);
        StringBuilder build = new StringBuilder();
        while(true){
            int h = input.nextInt();
            int w = input.nextInt();
            if(h==0&&w==0){
                break;
            }
            for(int n = 0; n < h; n++){
                for(int i = 0; i < w; i++){
                    if((n%2 == 1 && i%2 == 1) || (n%2 == 0 && i%2 == 0)){
                    build.append("#");
                    }else{
                    build.append(".");
                    }
                }
                build.append("\n");
            }
             build.append("\n");
        }
        System.out.print(build);
    }
}
/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