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