text: #include <iostream>
  #include <string>
  using namespace std;
  
  int main(){
    int h(0);
    int w(0);
    string pattern("");
  
    for(int i = 0; i < 300 * 2; i += 2){
      pattern += "#.";
    }
  
    while(1) {
      cin >> h >> w;
      if( h == 0 && w == 0 )
        break;
  
      for(int i = 0; i < h; ++i)
        cout << pattern.substr(i, w) << endl;
      cout << endl;
    }
    return 0;
  }
  
  