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