#include<iostream>
using namespace std;

int main(){
  while (true){
    int H, W;
    cin >> H >> W;
    if (H==0 && W==0) break;
    for (int i=1; i<=H; i++){
      for (int j=1; j<=W; j++){
	if (i%2 == j%2) cout << '#';
	else cout << '.';
      }
      cout << endl;
    }
    cout << endl;
  }
  return 0;
}