import java.util.Scanner;
public class Main {
   public static void main(String[] args){
     Scanner scanner = new Scanner(System.in);
     for(int i=1;i>0; i++){
          int H = scanner.nextInt();
          int W = scanner.nextInt();
          if(H==0&&W==0)break;
          for(int j=1;j<=H; j++){
              for(int k=1;k<=W; k++){
                  int l=(j+k)%2;
                if(l==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