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