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