import java.util.Scanner;

class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
  
    label:
    while(sc.hasNextLine()){
      int h = sc.nextInt();
      int w = sc.nextInt();
        
      if(h==0 && w==0) break label;
      for(int i = 1; i<=h; i++){
        for(int j = 1; j<=w; j++){
          if(i %2 != 0){             //?\???°???
            if(j % 2 != 0){
             System.out.print("#");
            }else{
              System.out.print(".");
            }
          }else if(i % 2 == 0){      //??¶??°???
            if(j % 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