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.print("#");
}else{
System.out.print(".");
}
}else{
if(j%2 == 0){
System.out.print(".");
}else{
System.out.print("#");
}
}
}
System.out.println();
}
System.out.println();
}
sc.close();
}
}
