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