import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;

public class Main {

	public static void main(String[] args) throws IOException{
		BufferedReader br = new BufferedReader(new InputStreamReader(System.in));

		while(true){
			String[] inputNum = br.readLine().split(" ");

			int H = Integer.parseInt(inputNum[0]);
			int W = Integer.parseInt(inputNum[1]);

			if (H == 0 && W == 0) {
				break;
			}

			for (int i = 0; i < H; i++) {
				for (int j = 0; j < W; j++) {
					if (((i%2 == 0) && (j%2 == 0)) || ((i%2 != 0) && (j%2 != 0))) {
						System.out.print("#");
					}else{
						System.out.print(".");
					}
				}
				System.out.println("");
			}

		}


	}

}