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 System.out.print(".");
                }
                System.out.println();
            }
        System.out.println();
        }
    }
}
