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