import java.util.Scanner;

public class Main {
    static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    }
} import java.util.Scanner; Scanner java.util public class Main {
    static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    }
} Main static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    } printBox {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    } char[] pat = {'#','.'}; pat {'#','.'} '#' '.' for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            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++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        } {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        } for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            } int j=0; int j=0; j 0 j<W j W j++ j++ j {
                System.out.print(pat[(i+j) % 2]);
            } {
                System.out.print(pat[(i+j) % 2]);
            } System.out.print(pat[(i+j) % 2]) System.out.print System.out System System.out pat[(i+j) % 2] pat (i+j) % 2 (i+j) i j 2 System.out.println("") System.out.println System.out System System.out "" System.out.println("") System.out.println System.out System System.out "" int H H int W W public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    } main {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    } Scanner in = new Scanner(System.in); in new Scanner(System.in) while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        } true {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        } int H = in.nextInt(); H in.nextInt() in.nextInt in int W = in.nextInt(); W in.nextInt() in.nextInt in if(H == 0) break; H == 0 H 0 break; printBox(H, W) printBox H W String[] args args public class Main {
    static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    }
} public class Main {
    static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    }
} Main
import java.util.Scanner;

public class Main {
    static void printBox(int H, int W) {
        char[] pat = {'#','.'};
        for(int i=0;i<H;i++) {
            for(int j=0;j<W;j++) {
                System.out.print(pat[(i+j) % 2]);
            }
            System.out.println("");
        }
        System.out.println("");
    }
    public static void main(String[] args) {
        Scanner in = new Scanner(System.in);
        while(true) {
            int H = in.nextInt();
            int W = in.nextInt();
            if(H == 0) break;
            printBox(H, W);
        }
    }
}