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