public class Main{
  public void run(java.io.InputStream in, java.io.PrintStream out){
    java.util.Scanner sc = new java.util.Scanner(in);
/*answer*/
    int h, w;
    int i, j;

    for(;;){
      h = sc.nextInt();
      w = sc.nextInt();
      if(h == 0 && w == 0)break;

      for(i = 0;i < h;i++){
        for(j = 0;j < w;j++){
          if((i + j) % 2 == 0){
            System.out.print("#");
          }else{
            System.out.print(".");
          }
        }
        System.out.println();
      }
      System.out.println();
    }

    sc.close();
  }
  public static void main(String[] args){
    (new Main()).run(System.in, System.out);
  }
}
/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