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();
        }
    }
}
