#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w, x, y;
  while (1) {
    y = 1;
    cin >> h >> w;
    if (h == 0 && w == 0) break;
    h, w <= 300;
    while (y <= h) {
      if (y >= 2) cout << endl;
      for (x = 1; x <= w; x++) {
        if (x % 2 == 0) {
          cout << ".";
        }
        if (x % 2 != 0) {
          cout << "#";
        }
      }
      y++;
    }
    cout << endl;
    cout << endl;
  }
}
