import java.util.Scanner;

public class Main{
    public static void main(String[] args){
        Scanner scan = new Scanner(System.in);
        int H,W,i,j;
        H=scan.nextInt();
        W=scan.nextInt();

        while(H!=0 || W!=0){
            for(i=0;i<H;i++){
                for(j=0;j<W;j++){
                    if((i%2==0 && j%2==0)||(i%2==1 && j%2==1)){
                        System.out.print("#");
                    }else{
                        System.out.print(".");
                    }
                }
                System.out.print("\n");
            }
            H=scan.nextInt();
            W=scan.nextInt();
        }

    }
}
