contract DiscountedPreICO is TimedCrowdsale {
  using SafeMath for uint256;
  
  function DiscountedPreICO(uint256 _opening_time, uint256 _closing_time) 
      TimedCrowdsale(_opening_time, _closing_time) public {
  }
  
  
  function _getTokenAmount(uint256 _weiAmount) internal view returns (uint256) {
     return _weiAmount.mul(rate).mul(100).div(100 - getCurrentDiscount());
  }
  
  /**
   * returns discount for the current time.
   */
  function getCurrentDiscount() public view returns(uint256) {
    return 0;
  }
}
function getCurrentDiscount() public view returns(uint256) {
  return 0;
}

/**
 * returns discount for the current time.
 */