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