import java.util.Scanner;

public class Main{
    public static void main(String[]arg){
        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.print("\n");
            }
        }
    }
}
