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.print('#');
                    else System.out.print('.');
                }
                System.out.println();
            }
            System.out.println();
        }
       
        sc.close();
    }
}

