#include<stdio.h>
int main(void)
{
	int h, w, H, W;

	while (1) {
		scanf("%d %d", &H, &W);
		for (h = 1; h <= H; h++)
		{
			if (H % 2 != 0) {
				for (w = 1; w <= (W / 2); w++) {
					printf("#.");
				}
			}
			else {
				for (w = 1; w <= (W / 2); w++) {
					printf("#.");
				}
			}
			printf("\n");
		}
		if (H == 0 && W == 0) break;
		printf("\n");
	}
	return 0;
