import java.util.Scanner;

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

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  }
} import java.util.Scanner; Scanner java.util public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int H; int W;

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  }
} Main public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int H; int W;

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  } main {
    Scanner scan = new Scanner(System.in);
    int H; int W;

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  } Scanner scan = new Scanner(System.in); scan new Scanner(System.in) int H; H int W; W do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0); H!=0 || W!=0 H!=0 H 0 W!=0 W 0 {
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } H = scan.nextInt() H scan.nextInt() scan.nextInt scan W = scan.nextInt() W scan.nextInt() scan.nextInt scan if(H==0 && W==0){break;} H==0 && W==0 H==0 H 0 W==0 W 0 {break;} break; StringBuilder sb1 = new StringBuilder(); sb1 new StringBuilder() StringBuilder sb2 = new StringBuilder(); sb2 new StringBuilder() for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      } int i=0; int i=0; i 0 i<W i W i++ i++ i {
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      } {
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      } if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");} i%2==0 i%2 i 2 0 {sb1.append("#"); sb2.append(".");} sb1.append("#") sb1.append sb1 "#" sb2.append(".") sb2.append sb2 "." {sb1.append("."); sb2.append("#");} sb1.append(".") sb1.append sb1 "." sb2.append("#") sb2.append sb2 "#" for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      } int j=0; int j=0; j 0 j<H j H j++ j++ j {
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      } {
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      } if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);} j%2==0 j%2 j 2 0 {System.out.println(sb1);} System.out.println(sb1) System.out.println System.out System System.out sb1 {System.out.println(sb2);} System.out.println(sb2) System.out.println System.out System System.out sb2 System.out.println("") System.out.println System.out System System.out "" String[] args args public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int H; int W;

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  }
} public class Main{
  public static void main(String[] args){
    Scanner scan = new Scanner(System.in);
    int H; int W;

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  }
} Main
import java.util.Scanner;

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

    do{
      H = scan.nextInt();
      W = scan.nextInt();
      if(H==0 && W==0){break;}

        //????????????????????????
      StringBuilder sb1 = new StringBuilder();//??¶??°??? ??????02468
      StringBuilder sb2 = new StringBuilder();//?\???°??? ??????13579
      for(int i=0; i<W; i++){
        if(i%2==0){sb1.append("#"); sb2.append(".");}
        else{sb1.append("."); sb2.append("#");}
      }

      for(int j=0; j<H; j++){
        if(j%2==0){System.out.println(sb1);}
        else {System.out.println(sb2);}
      }
      System.out.println("");
    } while(H!=0 || W!=0);
     
  }
}