import java.util.Scanner;
class Main{
  public static void main(String args[]){
    Scanner sc = new Scanner(System.in);
    while (true){
      int H = sc.nextInt();
      int W = sc.nextInt();
      if(H == 0 && W == 0){
        break;
      }
      for(int i = 0; i < H; i++){
        for(int j = 0; j < W; j++){
          if((i + j)%2 == 0){
            System.out.print("#");
          }else if((i + j) %2== 1){
            System.out.print(".");
          }
        }
        System.out.print("\n");
      }
System.out.print("\n");

    }
  }
}
