#include<stdio.h>
int main() {
	int n, m;
	while (scanf("%d %d", &n, &m), n + m) {
		for (int i = 0; i < n; i++) {
			for (int j = 0; j < m; j++)
				if ((i + j)%2==0)
					putchar('#');
				else putchar('.');
				puts("");
		}
		puts("");
	}
	return 0;
}