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%2+j)%2==0) System.out.printf("#");
                    else System.out.printf(".");
                }
                System.out.println();
            }
            System.out.println();
        }
        sc.close();
    }
}
