import java.util.Scanner;

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

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    }
}
 import java.util.Scanner; Scanner java.util public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    }
} Main public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    } main {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    } Scanner sc = new Scanner(System.in); sc new Scanner(System.in) while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            } true {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            } int w = sc.nextInt(); w sc.nextInt() sc.nextInt sc int h = sc.nextInt(); h sc.nextInt() sc.nextInt sc if (w + h == 0) {
                break;
            } w + h == 0 w + h w h 0 {
                break;
            } break; for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             } int a=0; int a=0; a 0 a<w a w ++a ++a a {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             } {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             } for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              } int b=0; int b=0; b 0 b<h b h ++b ++b b {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              } {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              } System.out.print(((a+b)%2==1 ? "." : "#")) System.out.print System.out System System.out ((a+b)%2==1 ? "." : "#") (a+b)%2==1 (a+b)%2 (a+b) a b 2 1 "." "#" System.out.println("") System.out.println System.out System System.out "" System.out.println("") System.out.println System.out System System.out "" sc.close() sc.close sc String[] args args public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    }
} public class Main{
    public static void main(String[] args) {
        Scanner sc = new Scanner(System.in);

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    }
} Main
import java.util.Scanner;

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

        while (true) {
            int w = sc.nextInt();
            int h = sc.nextInt();
            if (w + h == 0) {
                break;
            }

            for (int a=0; a<w; ++a) {
             for (int b=0; b<h; ++b) {
              System.out.print(((a+b)%2==1 ? "." : "#"));
              }
             System.out.println("");
             }
            System.out.println("");
            }
    sc.close();
    }
}

