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;
            }

            else{
                int i, j;

                for(i=1;i<=H;i++){
                    for(j=1;j<=W;j++){
                        if(i % 2 == j % 2){
                            System.out.print("#");
                        }
                        else{
                            System.out.print(".");
                        }
                    }
                    System.out.println();
                
                }   
            }      
        }

        sc.close();

    }

}

