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+j)%2==0)System.out.print("#");
else System.out.print(".");
}System.out.println(); }
System.out.println();}}}