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");
            }
        }
    }
}

