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