#include <bits/stdc++.h>
using namespace std;
int main() {
  int h;
  int w;
  int a;
  int b;
  while (true) {
    cin >> h >> w;
    if (h == 0 && w == 0) break;
    b = h;
    while (b > 0) {
      a = w;
      while (a > 0) {
        if ((a + b) % 2 == 0) {
          cout << ".";
        } else {
          cout << "#";
        }
        a--;
      }
      cout << endl;
      b--;
    }
    cout << endl;
  }
  return 0;
}
