import java.util.Scanner;

class Main {
    public static void main(String args[]) {
        Scanner scan = new Scanner(System.in);
        StringBuilder sb = new StringBuilder();

        while(true) {
            int H = scan.nextInt();
            int W = scan.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 ) {
                        sb.append(".");
                    } else {
                        sb.append("#");
                    }
                }
                sb.append("\n");
            }
            sb.append("\n");
        }
        System.out.print(sb);
    }

}