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%2 == 0 && j%2 == 0) || (i%2 == 1 && j%2 == 1)){
                  System.out.print("#");
               }else{
                  System.out.print(".");
               }
           }
           System.out.print("\n");
        }

       }
       sc.close();
    }
}
