#include <bits/stdc++.h>
using namespace std;
int main() {
  int h, w;
  char str[2][3] = {
      {"#."},
      {".#"},
  };
  while (cin >> h >> w, h | w) {
    for (int i = 0; i < h; i++) {
      for (int j = 0; j < w; j++) cout << str[i % 2][j % 2];
      cout << endl;
    }
  }
  return 0;
}
