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