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