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;
            }
            int i,j;
            for(i=0;i<H;i++){
                for (j=0;j<W;j++){
                    if((i+j)%2==0){
                        System.out.printf("#");
                    }else if((i+j)%2==1){
                        System.out.printf(".");
                    }
                }
                System.out.printf("\n");
            }
        }
        sc.close();
        System.out.printf("\n");
    }
}
