#include <bits/stdc++.h>
void drawChessboard(int height, int width);
int main(void) {
  int height;
  int width;
  while (1) {
    scanf("%d %d", &height, &width);
    if (height == 0 && width == 0) {
      break;
    }
    drawChessboard(height, width);
    printf("\n");
  }
  return 0;
}
void drawChessboard(int height, int width) {
  int i;
  int j;
  for (i = 0; i < height; i++) {
    for (j = 0; j < width; j++) {
      if (i + j % 2 == 0) {
        putchar('#');
      } else {
        putchar('.');
      }
    }
    printf("\n");
  }
  return;
}
