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