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