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