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