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((j+i)%2==0){
                         System.out.printf("#");
                     }else System.out.printf(".");
                 }
                 System.out.printf("\n");
             }
         }
    }
}
