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