#include <bits/stdc++.h>
int main(void) {
  int h, w, counth, countw = 0;
  while (1) {
    scanf("%d %d", &h, &w);
    if (h == 0 && w == 0) break;
    for (counth = 0; counth < h; counth++) {
      if (counth % 2 == 0) {
        while (countw < w) {
          printf("#");
          countw++;
          if (countw == w) break;
          printf(".");
          countw++;
        }
      } else
        while (countw < w) {
          printf(".");
          countw++;
          if (countw == w) break;
          printf("#");
          countw++;
        }
      printf("\n");
      countw = 0;
    }
  }
  return 0;
}
