import java.util.ArrayList;
import java.util.Scanner;

/**
 * Created 2017/06/08.
 */

public class Main {
  public static void main(String[] args) {

    //??\?????¨?????????
    Scanner sc = new Scanner(System.in);
    ArrayList<ArrayList<Integer>> ary_input = new ArrayList<>();
    while (true) {
      ArrayList<Integer> ary = new ArrayList<>();
      int input1 = Integer.parseInt(sc.next());
      int input2 = Integer.parseInt(sc.next());
      if (input1 == 0 && input2 == 0) break;
      ary.add(input1);
      ary.add(input2);
      ary_input.add(ary);
    }
    //System.out.println(ary_input);

    //??????????????????????´?????????????????????????
    ArrayList<ArrayList<StringBuilder>> ary_sb = new ArrayList<>();

    for (ArrayList<Integer> index : ary_input) {
      ary_sb.add(sisakuc(index.get(0), index.get(1)));
    }
    //System.out.println(ary_sb);

    //??¨?????¢???????????????
    for (int i = 0; i < ary_sb.size(); i++) {
      for (int j = 0; j < ary_sb.get(i).size(); j++) {
        System.out.println(ary_sb.get(i).get(j));
      }
      System.out.println("");
    }
  }

  //???????????????????????????(????????\??????????????§?????????

  public static ArrayList<StringBuilder> sisakuc(int a, int b) {
    ArrayList<StringBuilder> ary = new ArrayList<>();
    for (int i = 0; i < a; i++) {
      StringBuilder str1 = new StringBuilder("");
      for (int j = 0; j < b; j++) {
        int ci = i % 2;     //??????????????¨
        int cj = j % 2;     //??????????????¨
        if (ci == 0) {
          switch (cj) {
            case 0:
              str1 = str1.append("#");
              break;
            default:
              str1 = str1.append(".");
              break;
          }
        } else {
          switch (cj) {
            case 0:
              str1 = str1.append(".");
              break;
            default:
              str1 = str1.append("#");
              break;
          }
        }
      }
      ary.add(str1);
    }
    return ary;
  }
}
/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