import java.util.Scanner;


public class Main {
	public static void main(String[] args) {
		Scanner sc = new Scanner(System.in);
		int H;
		int W;
		
		while (true) {
			H = sc.nextInt();
			W = sc.nextInt();
			StringBuilder sb = new StringBuilder();
			
			//0 0?????????
			if (H ==0 && W ==0) {
				break;
			}

			for (int i = 0; i < H; i++) {
				for (int j = 0; j < W; j++) {
					//??????????????¶??°??????
					if(i%2 == 0){
						if(j%2 == 0){
							sb.append("#");
						}
						else {
							sb.append(".");
						}
					}
					//?????????????\???°??????
					if(i%2 != 0){
						if(j%2 == 0){
							sb.append(".");
						}
						else {
							sb.append("#");
						}
					}

				}
				//?¬??????????????????????
				sb.append("\n");
			}
			//??????
			System.out.println(sb);
		}
	}
}
/tmp/hf-datasets-cache/medium/datasets/42704881117311-config-parquet-and-info-qiankunmu-Project_CodeNet-896c9d36/hub/datasets--qiankunmu--Project_CodeNet_Python800_and_Java250/snapshots/c899fde44a77ba1cc14973ed3de064e4ff3aadc7/Project_CodeNet_Java250.tar.gz