#include <bits/stdc++.h>
int main() {
  int a, b;
  int c, d;
  for (;;) {
    scanf("%d %d", &a, &b);
    if (a == 0 && b == 0) break;
    for (c = 0; c < a; c++) {
      for (d = 0; d < b; d++) {
        if ((c + d) / 2 == 0) {
          printf("#");
        } else {
          printf(".");
        }
      }
      printf("\n");
    }
    printf("\n");
  }
  return 0;
}
