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) {
                System.out.printf("\n");
                break;
            }
            else for(int i = 0; i < H; i++){
                for(int j = 0; j < W; j++){
                    if((i+j) % 2 == 0){
                        System.out.printf("#\n");
                    } else {
                        System.out.printf(".\n");
                    }
                }
            }
        }
    }
}

