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