#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  int y, x;
  cin >> h;
  cin >> w;
  while (true) {
    cin >> h >> w;
    if (h == 0 && w == 0) {
      break;
    }
    for (y = 0; y < h; y++) {
      for (x = 0; x < w; x++) {
        if (y % 2 == 0) {
          if (x % 2 == 0) {
            cout << "#";
          } else {
            cout << ".";
          }
        } else {
          if (x % 2 == 0) {
            cout << ".";
          } else {
            cout << "#";
          }
        }
      }
      cout << "\n";
    }
    cout << "\n";
  }
  return 0;
}
