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