#include <bits/stdc++.h>
using namespace std;
int main() {
  int H, W, i, j, ans1, ans2;
  for (;;) {
    cin >> H >> W;
    if (H == 0 && W == 0) {
      break;
    }
    for (i = 1; i <= H; i++) {
      ans1 = i / 2 * 2;
      for (j = 1; j <= W; j++) {
        ans2 = j / 2 * 2;
        if ((ans1 != i) != (ans2 != j)) {
          cout << ".";
        } else {
          cout << "#";
        }
      }
      cout << endl;
    }
  }
  return 0;
}
