import java.util.*;
public class Main{
public static void main(String[] args){
while(true){
int H = nextInt();
int W = 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.println("#");
else System.out.println(".");}
}}
}}