import java.util.Scanner;

public class Main{
  public static void main(String[] args){
    Scanner sc = new Scanner(System.in);
    while(true){
      int H = sc.nextInt();
      int W = sc.nextInt();
      if(H==0&&W==0) break;
      for(int i=0;i<H;i++){
        for(int j=0;j<W;j++){
          if(i%2==0){
            if(j%2==0){
              System.out.printf("#");
            }else{
              System.out.printf(".");
            }
          }else{ 
            if(j%2==0){
              System.out.printf(".");
            }else{
              System.out.printf("#");
            }
          }
        }
         System.out.printf("\n");
      }
    }
  }
}