#include <bits/stdc++.h>
int main(void) {
  int H, W, i, j, f = 0;
  for (;;) {
    scanf("%d %d", &H, &W);
    if (H == 0 && W == 0) break;
    for (i = 1; i <= H; i++) {
      for (j = 1; j <= W; j++) {
        if (f)
          printf(".");
        else
          printf("#");
        f = !f;
      }
      printf("\n");
    }
    printf("\n");
  }
}
