import java.util.Scanner;

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

	while(true){
	    H = in.nextInt();
	    W = in.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.print("#");
			else System.out.print(".");
		    }else{
			if(j%2==0)System.out.print(".");
			else System.out.print("#");
		    }
		}
		System.out.println();  
	    }
	    System.out.println();  
	}
    }
}
	   

