import java.util.Scanner;

public class Main{
  public static void main(String[] args) {
    Scanner sc = new Scanner(System.in);

    int H, W, i, j, k;

    while(true){
      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.printf("#");
          else System.out.printf(".");
        }
        System.out.printf("\n");
      }

      System.out.printf("\n");
    }

  }
}

