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