import java.util.*;

public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    }
    
    private static void check(int h, int w) {
        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();
        }
    }
} import java.util.*; util.* java public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    }
    
    private static void check(int h, int w) {
        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();
        }
    }
} Main private static final Scanner scn = new Scanner(System.in); scn new Scanner(System.in) public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    } main {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    } int h h w; w while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        } (h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0 (h = scn.nextInt()) != 0 (h = scn.nextInt()) h scn.nextInt() scn.nextInt scn 0 (w = scn.nextInt()) != 0 (w = scn.nextInt()) w scn.nextInt() scn.nextInt scn 0 {
            check(h, w);
            System.out.println();
        } check(h, w) check h w System.out.println() System.out.println System.out System System.out String[] args args private static void check(int h, int w) {
        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();
        }
    } check {
        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();
        }
    } 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 int h h int w w public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    }
    
    private static void check(int h, int w) {
        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();
        }
    }
} public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    }
    
    private static void check(int h, int w) {
        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();
        }
    }
} Main
import java.util.*;

public class Main {
    private static final Scanner scn = new Scanner(System.in);
    
    public static void main(String[] args) {
        int h, w;
        while((h = scn.nextInt()) != 0 | (w = scn.nextInt()) != 0) {
            check(h, w);
            System.out.println();
        }
    }
    
    private static void check(int h, int w) {
        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();
        }
    }
}