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