#include <bits/stdc++.h>
using namespace std;
void print_chessboard(int H, int W);
string build_row(int W, string bw);
int main() {
  int H, W;
  while (cin >> H >> W) {
    if (H == 0 && W == 0) break;
    print_chessboard(H, W);
  }
}
void print_chessboard(int H, int W) {
  vector<string> rows{build_row(W, "#."), build_row(W, ".#")};
  for (int h = 0; h != H; ++h) {
    cout << rows[h % 2] << endl;
  }
  cout << endl;
}
string build_row(int W, string bw) {
  string row;
  for (int w = 0; w < W; w += 2) {
    row += bw;
  }
  if (W % 2) {
    row += bw[0];
  }
  return row;
}
