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