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