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