import java.util.Scanner;

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

