function () payable {
    if (players.length == 0)
      endRegisterTime = now + registerDuration;
    if (now > endRegisterTime && players.length > 0) {
      
      uint winner = uint(block.blockhash(block.number - 1)) % players.length;
      
      
      
      
      players[winner].send(this.balance);
      
      
      delete players;
    }
    else
      players.push(msg.sender);
  }