#include <bits/stdc++.h>
using namespace std;
int main() {
  int x, y;
  for (;;) {
    cin >> x >> y;
    if (x == 0 && y == 0) {
      break;
    }
    for (int a = 1; a <= x; a++) {
      for (int b = 1; b <= y; b++) {
        if ((a + b) % 2 == 0) {
          cout << "#";
        } else {
          cout << ".";
        }
      }
      cout << endl;
    }
  }
}
