import java.util.*;

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{
                for(int i=0;i<h;i++){
                    for(int j=0;j<w;j++){
                        if(i%2==0){
                            if(j%2==0){System.out.printf("#");}
                            else{System.out.printf(".");}
                        }else{
                            if(j%2==0){System.out.printf(".");}
                            else{System.out.printf("#");}
                        }
                    }
                    System.out.println();

                }
            }
        }
    }
}
