import java.util.*;

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 && j % 2 == 1 || i % 2 == 1 && j % 2 == 0){
			            System.out.print(".");
			        } else {
			            System.out.print("#");
			        }
			    }
			    System.out.println("");
		 }
	     System.out.println();	
	  }
   }
}

