#include <stdio.h>
int main(void) {
    int H, W, i, j;
    while (scanf("%d %d", &H, &W) == 2) {
        char pattern[W];
        if (H == 0 && W == 0) break;
        for (i = 0; i <= W / 2; i ++) {
            pattern[2i] = '#';
            pattern[2i + 1] = '.';
        }
        for (j = 0; j <= H - 1; j ++) {
            if (j % 2 == 0) {
                for (i = 0; i <= W - 1; i ++) printf("%c", pattern[i]);
                print("\n");
            }
            if (j % 2 == 1) {
                for (i = W - 1; i >= 0; i --) printf("%c", pattern[i]);
                printf("\n");
            }
        }
    }
    return 0;
}