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