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