import java.util.*;

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();
		}
    }
}
