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