import java.util.Scanner;

public class Main {
    public static void main(String[] args){
        Scanner sc = new Scanner(System.in);

        int H, W;
        H = sc.nextInt();
        W = sc.nextInt();

        if(H == 0 && W == 0)
            return;

        while(H != 0 || W != 0){
            for(int i = 0; i < H; i++){
                for(int j = 0; j < W; j++){
                    if(i % 2 == 0 && j % 2 == 0)
                        System.out.print("#");
                    else
                        System.out.print(".");
                }
                System.out.println();
            }

            H = sc.nextInt();
            W = sc.nextInt();
        }

    }
}
