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++){
                System.out.print((i+j)%2==0 ? '#' : '.');
            }
             System.out.println();
         }
        System.out.print("\n");
        }
        sc.close();
    }
}
    
