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