function start (uint _maxTime, uint _addedTime) public restricted {
    require(startTime == 0);
    require(_maxTime > 0 && _addedTime > 0);
    require(_maxTime > _addedTime);

    maxTime = _maxTime;
    addedTime = _addedTime;

    startTime = block.timestamp;
    endTime = startTime + maxTime;
    addressOfCaptain = addressOfOwner;

    _registerReferral("owner", addressOfOwner);

    emit Started(startTime);
  }