import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    }
} import java.util.Scanner; Scanner java.util public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    } main {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) int h = sc.nextInt(); h sc.nextInt() sc.nextInt sc int w = sc.nextInt(); w sc.nextInt() sc.nextInt sc while(h != 0 || w != 0){
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    if((i+j)%2==0){
                        System.out.print("#");
                    }else{
                        System.out.print(".");

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        } h != 0 || w != 0 h != 0 h 0 w != 0 w 0 {
            for (int i = 0; i < h; i++) {
                for (int j = 0; j < w; j++) {
                    if((i+j)%2==0){
                        System.out.print("#");
                    }else{
                        System.out.print(".");

                    }
                }
                System.out.println("");
            }
            System.out.println("");

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

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

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

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

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

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

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

                    } (i+j)%2==0 (i+j)%2 (i+j) i j 2 0 {
                        System.out.print("#");
                    } System.out.print("#") System.out.print System.out System System.out "#" {
                        System.out.print(".");

                    } System.out.print(".") System.out.print System.out System System.out "." System.out.println("") System.out.println System.out System System.out "" System.out.println("") System.out.println System.out System System.out "" h = sc.nextInt() h sc.nextInt() sc.nextInt sc w = sc.nextInt() w sc.nextInt() sc.nextInt sc sc.close() sc.close sc String[] args args public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    }
} public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    }
} Main
import java.util.Scanner;

public class Main {
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        int h = sc.nextInt();
        int w = sc.nextInt();

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

                    }
                }
                System.out.println("");
            }
            System.out.println("");

            h = sc.nextInt();
            w = sc.nextInt();
            
        }


        sc.close();
    }
}
