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 == 0){
                        if(j%2 == 0){
                            System.out.print("#");
                        }else{
                            System.out.print(".");
                        }
                    }else{
                        if(j%2 == 0){
                            System.out.print(".");
                        }else{
                            System.out.print("#");
                    }
                }
            }
            System.out.print("\n");
        }
    }
}
}
