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