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